Breaking the core-envelope symmetry in p-mode pulsating stars

It has been shown that there is a potential ambiguity in the asteroseismic determination of the location of internal structures in a pulsating star. We show how, in the case of high-order non-radial acoustic modes, it is possible to remove this ambiguity by considering modes of different degree. To support our conclusions we have investigated the seismic signatures of sharp density variations in the structure of quasi-homogeneous models.Comment: 3 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

Traceability Adoption at the Farm Level: An Empirical Analysis of the Portuguese Pear Industry

Traceability is becoming a condition for doing business in European food markets. Retailers are adopting standards that are more stringent than what is mandatory. An example is EurepGAP, a quality standard for good agricultural practices that includes traceability as a main requirement. We analyze EurepGAP implementation in the Portuguese pear industry and find that implementation cannot be distinguished from sales to British supermarkets. Discrete choice models show the odds of traceability adoption increase with farm size and previous compliance with quality assurance schemes, while farm productivity has a negative impact on the probability of adoption.Research and Development/Tech Change/Emerging Technologies,

Distributional approach to point interactions in one-dimensional quantum mechanics

We consider the one-dimensional quantum mechanical problem of defining interactions concentrated at a single point in the framework of the theory of distributions. The often ill-defined product which describes the interaction term in the Schr\"odinger and Dirac equations is replaced by a well-defined distribution satisfying some simple mathematical conditions and, in addition, the physical requirement of probability current conservation is imposed. A four-parameter family of interactions thus emerges as the most general point interaction both in the non-relativistic and in the relativistic theories (in agreement with results obtained by self-adjoint extensions). Since the interaction is given explicitly, the distributional method allows one to carry out symmetry investigations in a simple way, and it proves to be useful to clarify some ambiguities related to the so-called $\delta^\prime$ interaction.Comment: Open Access link: http://journal.frontiersin.org/Journal/10.3389/fphy.2014.00023/abstrac

The dynamics of corporate credit risk: an intensity-based econometric analysis

Lucas, A. [Promotor

Optimal choice of Voluntary traceability as a food risk management tool

Traceability systems are information tools implemented within and between firms in food chains to improve logistics and transparency or to reduce total food safety damage costs. Information about location and condition of products is critical when food safety incidents arise. This paper uses a principal-agent model to investigate the optimal choice of voluntary traceability in terms of precision of information on a given attribute at each link of a food chain. The results suggest that four scenarios may emerge for the supply chain depending on the costs of a system and whether or not the industry can internalize total food safety damages: no traceability, traceability for one link, equal traceability for all links, or different positive traceability levels across all links.Traceability, food safety, principal-agent model, Food Consumption/Nutrition/Food Safety,

Dynamics of a yoyo using a smartphone gyroscope sensor

The dynamics of a traditional toy, the yoyo, is investigated theoretically and experimentally using smartphone' sensors. In particular, using the gyroscope the angular velocity is measured. The experimental results are complemented thanks to a digital video analysis. The concordance between theoretical and experimental results is discussed. As the yoyo is a ubiquitous, simple and traditional toy this simple proposal could encourage students to experiment with everyday objects and modern technologies.Comment: 10 pages, 5 figures, typos and added a discussion about classroom implementation

The Economics of Traceability for Multi-Ingredient Products: A Network Approach

The consumption of multi-ingredient foods is increasing across the globe as consumers spend less time preparing meals. Traceability is now extensively used to reduce information imperfections in food markets and recent EU law suggests it will be implemented for manufactured meals as well. We present a model developed to understand how information on different ingredients flows through supply chains for multi-ingredient food products. The network model has three tiers linked by contracts for levels of quality and information. The model is useful for analyzing tradeoffs and network effects emerging in the choice of traceability levels.Traceability, multi-ingredient foods, network models, Food Consumption/Nutrition/Food Safety,

Some boundary effects in quantum field theory

We have constructed a quantum field theory in a finite box, with periodic boundary conditions, using the hypothesis that particles living in a finite box are created and/or annihilated by the creation and/or annihilation operators, respectively, of a quantum harmonic oscillator on a circle. An expression for the effective coupling constant is obtained showing explicitly its dependence on the dimension of the box.Comment: 12 pages, Late