How realistic are solar model atmospheres?

Recently, new solar model atmospheres have been developed to replace classical 1D LTE hydrostatic models and used to for example derive the solar chemical composition. We aim to test various models against key observational constraints. In particular, a 3D model used to derive the solar abundances, a 3D MHD model (with an imposed 10 mT vertical magnetic field), 1D models from the PHOENIX project, the 1D MARCS model, and the 1D semi-empirical model of Holweger & M\"uller. We confront the models with observational diagnostics of the temperature profile: continuum centre-to-limb variations (CLV), absolute continuum fluxes, and the wings of hydrogen lines. We also test the 3D models for the intensity distribution of the granulation and spectral line shapes. The predictions from the 3D model are in excellent agreement with the continuum CLV observations, performing even better than the Holweger & M\"uller model (constructed largely to fulfil such observations). The predictions of the 1D theoretical models are worse, given their steeper temperature gradients. For the continuum fluxes, predictions for most models agree well with the observations. No model fits all hydrogen lines perfectly, but again the 3D model comes ahead. The 3D model also reproduces the observed continuum intensity fluctuations and spectral line shapes very well. The excellent agreement of the 3D model with the observables reinforces the view that its temperature structure is realistic. It outperforms the MHD simulation in all diagnostics, implying that recent claims for revised abundances based on MHD modelling are premature. Several weaknesses in the 1D models are exposed. The differences between the PHOENIX LTE and NLTE models are small. We conclude that the 3D hydrodynamical model is superior to any of the tested 1D models, which gives further confidence in the solar abundance analyses based on it.Comment: 17 pages, 15 figures. Accepted for publication in A&

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

Trouble at the top: The construction of a tenant identity in the governance of social housing organizations

The project of citizen governance has transformed the social housing sector in England where 20,000 tenants now sit as directors on the boards of housing associations, but the entrance of social housing tenants to the boardroom has aroused opposition from the chief executives of housing companies and triggered regulatory intervention from government inspectors. This paper investigates the cause of these tensions through a theoretical framework drawn from the work of feminist philosopher Judith Butler. It interprets housing governance as an identificatory project with the power to constitute tenant directors as regulated subjects, and presents evidence to suggest that this project of identity fails to completely enclose its subject, allowing tenant directors to engage in ‘identity work’ that threatens the supposed unity of the board. The paper charts the development of antagonism and political tension in the board rooms of housing companies to present an innovative account of the construction and contestation of identities in housing governance

Universal Rights and Wrongs

This paper argues for the important role of customers as a source of competitive advantage and firm growth, an issue which has been largely neglected in the resource-based view of the firm. It conceptualizes Penrose’s (1959) notion of an ‘inside track’ and illustrates how in-depth knowledge about established customers combines with joint problem-solving activities and the rapid assimilation of new and previously unexploited skills and resources. It is suggested that the inside track represents a distinct and perhaps underestimated way of generating rents and securing long-term growth. This also implies that the sources of sustainable competitive advantage in important respects can be sought in idiosyncratic interfirm relationships rather than within the firm itself

Simulation of dimensionality effects in thermal transport

The discovery of nanostructures and the development of growth and fabrication techniques of one- and two-dimensional materials provide the possibility to probe experimentally heat transport in low-dimensional systems. Nevertheless measuring the thermal conductivity of these systems is extremely challenging and subject to large uncertainties, thus hindering the chance for a direct comparison between experiments and statistical physics models. Atomistic simulations of realistic nanostructures provide the ideal bridge between abstract models and experiments. After briefly introducing the state of the art of heat transport measurement in nanostructures, and numerical techniques to simulate realistic systems at atomistic level, we review the contribution of lattice dynamics and molecular dynamics simulation to understanding nanoscale thermal transport in systems with reduced dimensionality. We focus on the effect of dimensionality in determining the phononic properties of carbon and semiconducting nanostructures, specifically considering the cases of carbon nanotubes, graphene and of silicon nanowires and ultra-thin membranes, underlying analogies and differences with abstract lattice models.Comment: 30 pages, 21 figures. Review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.

Embryogenesis in microspore culture of Vitis subspecies

Embryoid structures showing epidermal layers have been regenerated from isolated Vitis microspores. Experiments were carried out on 8 genotypes of Vitis including different donor plant growth conditions, chilling of microspores (4 °C), heat shock (35 °C) and colchicine exposure (10, 25 and 50 mg/l) as induction treatments and incubation of the cultures on 87 different solid and liquid NN and LS media. The reactions of the cultured microspores included enlargement and thickening of the exine, formation of microcalli, calli, globular proembryos and embryoid structures displaying cell differentiation. Callus formation took place mainly on solid LS media with 3 % or 12 % sucrose, whereas most of the embryoids developed on NN media with 3 % sucrose. Both, callus and embryoid formation, were promoted by colchicine treatment. 8 months after transfer of calli and embryoids to subculture media, 4 embryoids still showed cell proliferation

Considering Stress in a Nursing Student Context: Pre-Admission to Pre-Graduation

In moderation, stress is a normal response to a perceived challenge which can motivate an individual to perform at their best. Nursing students consistently report a significant amount of stress which has been found to be greater than their non-nursing peers. The purpose of this study is to assess the level of stress reported by second-semester freshman and sophomore students who have declared nursing as a major, compared with the level of stress experienced by junior and senior students who are enrolled in the university\u27s nursing program. Through this comparison, a conclusion can be drawn as to the level of stress experienced while enrolled in a nursing program, with the level of stress prior to being exposed to the challenges presented by the program. It is intended that the outcomes from this study can be utilized to address stress as it relates to a nursing student from pre-admission through graduation

Travelers With Cutaneous Leishmaniasis Cured Without Systemic Therapy

Guidelines recommend wound care and/or local therapy as first-line treatment for cutaneous leishmaniasis. An analysis of a referral treatment program in 135 travelers showed that this approach was feasible in 62% of patients, with positive outcome in 83% of evaluable patient

Application of microsatellite markers to parentage studies in grapevine

The use of microsatellites in genetic analysis does not only allow differentiation but also identification and parentage analysis of grapevine cultivars. Many of the cultivars which are of great economic importance, like Cabernet Sauvignon, have been selected and propagated centuries ago and often lack reliable documentation about their origins. In our study, 51 grapevine cultivars were genotyped at 24 microsatellite loci and searched for possible parent-offspring combinations. Our data confirm the origin of Cabernet Sauvignon from a cross between Cabernet franc and Sauvignon blanc. Furthermore we proved the parentage of the cultivars Neuburger (Silvaner x Veltliner rot), Blauburger (Portugieser blau x Blaufränkisch), Zweigelt (Blaufränkisch x St. Laurent) and Müller-Thurgau (Rheinriesling x Chasselas de Courtillier) at 24 SSR loci

Deepening inside the homonyms of 'Wildbacher' by means of SSR markers

Sixteen accessions of the grapevine cultivar 'Wildbacher' coming from different European repositories and from Styrian and Italian private vineyards were analysed by genetic fingerprinting with SSR markers. Five different molecular profiles were found, confirming that the name 'Wildbacher' is commonly used as a homonym. Several new genotypes could be linked to the previous list of the 'Wildbacher' family. In particular, in Italian commercial vineyards two main 'Wildbacher' varieties defined by A and B genetic profiles were found. They correspond to the two reference genotypes from Styria, 'Wildbacher Blau' ('Blauer Wildbacher)' and 'Wildbacher Spätblau'. In both countries 'Wildbacher Blau' represents the most spread and better performing type and it is earlier ripening compared to 'Wildbacher Spätblau'. They were morphologically and genetically very similar to each other and they shared at least one allele at each of the 11 SSR loci analyzed for cultivar identification. Three different other 'Wildbacher' genotypes from a German collection were identified as individual cultivars. While 'Rotblättriger' (genotype C) and 'Frühblau' from Germany (genotype D) showed some genetic similarity with A and B genotypes, E 'Wildbacher', coming from Hungary, proved to have a distinct genetic profile. Close relationship to the key variety (for the development of European diversity) 'Heunisch' is indicated by sharing one allele at all loci investigated so far. There exist some indications that the second parent is an extinct wild vine. Evaluation of morphological parameters resulted in some differences among all five genotypes.