The Optimal Gravitational Lens Telescope

Given an observed gravitational lens mirage produced by a foreground deflector (cf. galaxy, quasar, cluster,...), it is possible via numerical lens inversion to retrieve the real source image, taking full advantage of the magnifying power of the cosmic lens. This has been achieved in the past for several remarkable gravitational lens systems. Instead, we propose here to invert an observed multiply imaged source directly at the telescope using an ad-hoc optical instrument which is described in the present paper. Compared to the previous method, this should allow one to detect fainter source features as well as to use such an optimal gravitational lens telescope to explore even fainter objects located behind and near the lens. Laboratory and numerical experiments illustrate this new approach

Rethinking Service Design: A Socio-Technical Approach to the Development of Business Models

This chapter introduces socio-technical systems thinking as a tool for the concurrent development of organizational business models and associated service offerings that deliver value to customers and suppliers. As organizations offer integrated products and services, interactions and relationships between customer and supplier have assumed greater importance. Traditionally, importance was placed on the customer need and requirements for a physical product. Socio-technical systems thinking advocates a holistic perspective of complex work systems, ensuring the consideration of both technical and social aspects of a system. As illustrated through the three case studies in this chapter, product-service systems are becoming increasingly common within organizations. The first discusses the growing trend for manufacturing organizations to move from traditional transactional business models, with a focus on the delivery of physical products, to the inclusion of service delivery. The second case study provides details of manufacturing supply networks and the associated changing business models needed to support the development of supplier capability. Finally, the third case study considers changing business models and service delivery in the emerging context of technology-intensive healthcare services in the UK. To conclude, a socio-technical framework is proposed as a tool to aid in the development of business models and service delivery using these case studies as examples

New approach for precise computation of Lyman-alpha forest power spectrum with hydrodynamical simulations

Current experiments are providing measurements of the flux power spectrum from the Lyman-α forests observed in quasar spectra with unprecedented accuracy. Their interpretation in terms of cosmological constraints requires specific simulations of at least equivalent precision. In this paper, we present a suite of cosmological N-body simulations with cold dark matter and baryons, specifically aiming at modeling the low-density regions of the inter-galactic medium as probed by the Lyman-α forests at high redshift. The simulations were run using the GADGET-3 code and were designed to match the requirements imposed by the quality of the current SDSS-III/BOSS or forthcoming SDSS-IV/eBOSS data. They are made using either 2 × 7683 1 billion or 2 × 1923 14 million particles, spanning volumes ranging from (25 Mpc h−1)3 for high-resolution simulations to (100 Mpc h−1)3 for large-volume ones. Using a splicing technique, the resolution is further enhanced to reach the equivalent of simulations with 2 × 30723 58 billion particles in a (100 Mpc h−1)3 box size, i.e. a mean mass per gas particle of 1.2 × 105M⊙ h−1. We show that the resulting power spectrum is accurate at the 2% level over the full range from a few Mpc to several tens of Mpc. We explore the effect on the one-dimensional transmitted-flux power spectrum of four cosmological parameters (ns, σ8, Ωm and H0) and two astrophysical parameters (T0 and γ) that are related to the heating rate of the intergalactic medium. By varying the input parameters around a central model chosen to be in agreement with the latest Planck results, we built a grid of simulations that allows the study of the impact on the flux power spectrum of these six relevant parameters. We improve upon previous studies by not only measuring the effect of each parameter individually, but also probing the impact of the simultaneous variation of each pair of parameters. We thus provide a full second-order expansion, including cross-terms, around our central model. We check the validity of the second-order expansion with independent simulations obtained either with different cosmological parameters or different seeds. Finally, a comparison to the one-dimensional Lyman-α forest power spectrum obtained with BOSS by [1] shows an excellent agreement

ARCRAIDER II: Arc search in a sample of non-Abell clusters

We present a search for gravitational arcs in a sample of X-ray luminous, medium redshift clusters of galaxies. The sample of clusters is called ARCRAIDER, is based on the ROSAT Bright Survey (RBS) and fulfills the following criteria: (a) X-ray luminosity Lx>=0.5x10^45erg/s (0.5-2keV band), (b) redshift range 0.1<=z<=0.52, (c) classified as clusters in the RBS, (d) not a member of the Abell catalogue and, finally, (e) visible from the ESO sites La Silla/Paranal (declination \delta<=20deg). In total we found more than 35 (giant) arc/arclet candidates, including a possible radial arc, one galaxy-galaxy lensing event and a possible quasar triple image in 14 of the 21 clusters of galaxies. Hence 66% of the sample members are possible lenses.Comment: Accepted for publication in Astronomy and Astrophysics; 8 pages (excl. Appendix), 6 figures, 9 tables; Please download the high-res images of the appendix from http://astro-staff.uibk.ac.at/~w.kausch/ARCRAIDER_II_images.tar.g

Pay What You Want as a Marketing Strategy in Monopolistic and Competitive Markets

Pay What You Want (PWYW) can be an attractive marketing strategy to price discriminate between fair-minded and selfish customers, to fully penetrate a market without giving away the product for free, and to undercut competitors that use posted prices. We report on laboratory experiments that identify causal factors determining the willingness of buyers to pay voluntarily under PWYW. Furthermore, to see how competition affects the viability of PWYW, we implement markets in which a PWYW seller competes with a traditional seller. Finally, we endogenize the market structure and let sellers choose their pricing strategy. The experimental results show that outcome-based social preferences and strategic considerations to keep the seller in the market can explain why and how much buyers pay voluntarily to a PWYW seller. We find that PWYW can be viable in isolation, but it is less successful as a competitive strategy because it does not drive traditional posted-price sellers out of the market. Instead, the existence of a posted-price competitor reduces buyers’ payments and prevents the PWYW seller from fully penetrating the market. If given the choice, the majority of sellers opt for setting a posted price rather than a PWYW pricing. We discuss the implications of these results for the use of PWYW as a marketing strategy

K2: A new method for the detection of galaxy clusters based on CFHTLS multicolor images

We have developed a new method, K2, optimized for the detection of galaxy clusters in multicolor images. Based on the Red Sequence approach, K2 detects clusters using simultaneous enhancements in both colors and position. The detection significance is robustly determined through extensive Monte-Carlo simulations and through comparison with available cluster catalogs based on two different optical methods, and also on X-ray data. K2 also provides quantitative estimates of the candidate clusters' richness and photometric redshifts. Initially K2 was applied to 161 sq deg of two color gri images of the CFHTLS-Wide data. Our simulations show that the false detection rate, at our selected threshold, is only ~1%, and that the cluster catalogs are ~80% complete up to a redshift of 0.6 for Fornax-like and richer clusters and to z ~0.3 for poorer clusters. Based on Terapix T05 release gri photometric catalogs, 35 clusters/sq deg are detected, with 1-2 Fornax-like or richer clusters every two square degrees. Catalogs containing data for 6144 galaxy clusters have been prepared, of which 239 are rich clusters. These clusters, especially the latter, are being searched for gravitational lenses -- one of our chief motivations for cluster detection in CFHTLS. The K2 method can be easily extended to use additional color information and thus improve overall cluster detection to higher redshifts. The complete set of K2 cluster catalogs, along with the supplementary catalogs for the member galaxies, are available on request from the authors.Comment: Accepted in ApJ. 25 pages, including 10 figures. Latex with emulateapj v03/07/0

The impact of temperature fluctuations on the large-scale clustering of the Lyα forest

We develop a semi-analytic method for assessing the impact of the large-scale IGM temperature fluctuations expected following He ii reionization on three-dimensional clustering measurements of the Lyα forest. Our methodology builds upon the existing large volume, mock Lyα forest survey simulations presented by Greig et al. by including a prescription for a spatially inhomogeneous ionizing background, temperature fluctuations induced by patchy He ii photoheating and the clustering of quasars. This approach enables us to achieve a dynamic range within our semi-analytic model substantially larger than currently feasible with computationally expensive, fully numerical simulations. The results agree well with existing numerical simulations, with large-scale temperature fluctuations introducing a scale-dependent increase in the spherically averaged 3D Lyα forest power spectrum of up to 20–30 per cent at wavenumbers k ∼ 0.02 Mpc− 1. Although these large-scale thermal fluctuations will not substantially impact upon the recovery of the baryon acoustic oscillation scale from existing and forthcoming dark energy spectroscopic surveys, any complete forward modelling of the broad-band term in the Lyα correlation function will none the less require their inclusion

Signatures of reionization on Lyman alpha emitters

We use a semi-analytic model of Lyman alpha emitters (LAEs) to constrain the reionization history. By considering two physically motivated scenarios in which reionization ends either early (ERM, z_i ~ 7) or late (LRM, z_i ~ 6), we fix the global value of the IGM neutral fraction (e.g. chi_{HI}=3 times 10^{-4}, 0.15 at z=6.56 for the ERM and LRM, respectively) leaving only the star formation efficiency and the effective escape fraction of Lya photons as free parameters. The ERM fits the observed LAE luminosity function (LF) at z=5.7 and 6.56 requiring no redshift evolution or mass dependence of the star formation efficiency, and LAE star formation rates (SFR) of 3-103 solar masses/year, contributing approximately 8% of the cosmic SFR density at z=5.7. The LRM requires a physically uncomfortable drop of approximately 4.5 times in the SFR of the emitters from z=6.5 to 5.7. Thus, the data seem to imply that the Universe was already highly ionized at z=6.56. The mass-dependent Lya transmissivity is between 0.36-0.51 (ERM) and less than 0.26 (LRM) at z=6.56. The LF data at z=4.5 imply an extra Lya line damping factor of approximately 0.25 possibly due to dust; the presence of a (clumpy) dust component with E(B-V) ~ 0.28 is also required to reproduce the observed large Lya equivalent widths at the same redshift. Additional useful information can be extracted from the line profile (weighted) skewness, found to be S_W=10-17 Angstrom for the two reionization models, which shows an interesting L_alpha-chi_{HI} anti-correlation, holding under the model assumptions. The shortcomings of the model and strategies to overcome them are discussed.Comment: 15 pages, 10 figures, Accepted to MNRA

Secular changes in severity of intellectual disability in tuberous sclerosis complex: A reflection of improved identification and treatment of epileptic spasms?

Tuberous sclerosis complex (TSC) is a multisystem genetic disorder caused by mutations in TSC1 or TSC2. Epilepsy occurs in 80%-90% of affected individuals during their lifetime, and up to one-third of children with TSC will develop epileptic (infantile) spasms, for which vigabatrin has been shown to be particularly effective. Epilepsy severity and epileptic spasms are consistent markers of risk for the development of intellectual impairment in TSC. Although previous studies demonstrate a bimodal distribution of intellectual ability in TSC, recent findings suggest a unimodal distribution, which may reflect a change in IQ distribution over time. We compared 3 large historical UK cohorts of TSC (n = 331) that show varied distributions of intellectual ability, first ruling out differences in study methodology. Later-born individuals had a higher frequency of reported spasms and higher likelihood of vigabatrin administration, but were less likely to have profound intellectual impairment, compared to the earlier-born individuals. Our findings suggest that epileptic spasms went undetected in the older patients and therefore were not treated, leading to a higher occurrence of profound impairment, whereas the later born cohort had better access to treatment. These findings support the importance of early identification and treatment of seizures in TSC