Wavefront curvature sensing for the human eye

In this paper we present a curvature wavefront sensor for the eye. The layout proposed is novel, whilst the algorithm used has been adapted from previously published work [Roddier, F.; Roddier, C. Appl. Opt. 1991, 30, 1325–1327]. The design of the set-up incorporates two field lenses that, together with a beam separator, define the distance Δz between the two sampled planes. We present a feasibility study to use this particular combination of optical configuration and retrieval algorithm in the eye. We present calibration curves and results from three real eyes

Effects of gluon number fluctuations on photon - photon collisions at high energies

We investigate the effects of gluon number fluctuations on the total $\gamma\gamma$, $\gamma^*\gamma^*$ cross sections and the photon structure function $F_2^\gamma(x,Q^2)$. Considering a model which relates the dipole-dipole and dipole-hadron scattering amplitudes, we estimate these observables by using event-by-event and physical amplitudes. We demonstrate that both analyses are able to describe the LEP data, but predict different behaviours for the observables at high energies, with the gluon fluctuations effects decreasing the cross sections. We conclude that the study of $\gamma \gamma$ interactions can be useful to constrain the QCD dynamics.Comment: 9 pages, 6 figures. Improved version with two new figures. Version to be published in Physical Review

Propuesta para un Proyecto de Evaluación de Stocks de Camarón de Profundidad en aguas de Cabo Verde (2010-2013)

A bibliographic revision on the fisheries research in the Canary, Madeira, and the Azores Islands related to stock assessment of the striped soldier shrimp (Plesionika edwardsii) (Crustacea, Decapoda, Pandalidae) was made. Biological information –reproduction, growth, mortality, recruitment– of the target species, selective technological developments –multiple semi-floating shrimp traps–, and know-how gained by the ICCM can give support to elaborate and execute an ICCM-INDP joint project, in order to explore and assess its insular stocks in the Capeverdian deepwaters (150-300 m). In the frame of the UE Trans-national Cooperation Programme MAC (2007- 2013), the next coming call for proposals seems to be an adequate source to fund it. This project should include some activities for the valorisation and promotion of this new shellfish product, as well as for scientific-technical and social divulgation, and for giving advice to the decision-makers. Lastly, with the aim of developing a new fishing activity in the Cape Verdes on a responsible and sustainable basis, authors have scheduled a second study phase. This should consist of a process of technology transfer, followed by an experimental fishing pilot project including a study on biological and commercial viability with the participation of the Capeverdian fishing sector

γ∗p\gamma^*p cross section from the dipole model in momentum space

We reproduce the DIS measurements of the proton structure function at high energy from the dipole model in momentum space. To model the dipole-proton forward scattering amplitude, we use the knowledge of asymptotic solutions of the Balitsky-Kovchegov equation, describing high-energy QCD in the presence of saturation effects. We compare our results with the previous analysis in coordinate space and discuss possible extensions of our approach.Comment: 9 pages, 3 figure

Perfect category-graded algebras

In a perfect category every object has a minimal projective resolution. We give a criterion for the category of modules over a categorygraded algebra to be perfect.Comment: A sufficient condition is replaced by a criterion. Several references added. 17 page

An Experimental Study in Adaptive Kernel Selection for Bayesian Optimization

Bayesian Optimization has been widely used along with Gaussian Processes for solving expensive-to-evaluate black-box optimization problems. Overall, this approach has shown good results, and particularly for parameter tuning of machine learning algorithms. Nonetheless, Bayesian Optimization has to be also configured to achieve the best possible performance, being the selection of the kernel function a crucial choice. This paper investigates the convenience of adaptively changing the kernel function during the optimization process, instead of fixing it a priori. Six adaptive kernel selection strategies are introduced and tested in well-known synthetic and real-world optimization problems. In order to provide a more complete evaluation of the proposed kernel selection variants, two major kernel parameter setting approaches have been tested. According to our results, apart from having the advantage of removing the selection of the kernel out of the equation, adaptive kernel selection criteria show a better performance than fixed-kernel approaches

in-depth analysis of SVM kernel learning and its components

The performance of support vector machines in non-linearly-separable classification problems strongly relies on the kernel function. Towards an automatic machine learning approach for this technique, many research outputs have been produced dealing with the challenge of automatic learn- ing of good-performing kernels for support vector machines. However, these works have been carried out without a thorough analysis of the set of components that influence the behavior of support vector machines and their interaction with the kernel. These components are related in an in- tricate way and it is difficult to provide a comprehensible analysis of their joint effect. In this paper we try to fill this gap introducing the necessary steps in order to understand these interactions and provide clues for the research community to know where to place the emphasis. First of all, we identify all the factors that affect the final performance of support vector machines in relation to the elicitation of kernels. Next, we analyze the factors independently or in pairs and study the influence each component has on the final classification performance, providing recommendations and insights into the kernel setting for support vector machines.IT1244-19 PID2019-104966GB-I0

IFRS accounting quality in Latin America: A comparison with anglo-saxon and continental European countries and the role of cross-listing in the U.S.

This study analyses the level of IFRS accounting quality in Latin America, when compared to Anglo-Saxon and Continental European countries. It also analyses the role of crosslisting in the US when comparing the level of accounting quality of Latin American firms with foreign firms. Prior literature has focused on developed countries. There is a lack of knowledge about less developed countries, especially in Latin America, despite their relevant role on the global economy. This paper fills this gap in the literature by analysing the level of IFRS accounting quality in the main Latin American Countries applying IFRS (Brazil and Chile), when compared to the main Anglo-Saxon countries with IFRS tradition (United Kingdom and Australia), but also when compared with the main European Continental economies (France and Germany). The results show that Latin American firms present a lower level of accounting quality, even when only those firms cross-listed in the U.S., regarded as global players, are compared. Thus, even with a unique set of high quality accounting standards (IFRS) and strong reporting incentives, countries’ specific characteristics still play an important role in the way as IFRS are applied.info:eu-repo/semantics/submittedVersio

Análise econômica dos sistemas de cultivo com Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby (Paricá) e Ananas comosus var. erectifolius (L. B. Smith) Coppus & Leal (Curauá) no município de Aurora do Pará (pa), Brasil.

O objetivo do trabalho foi analisar a viabilidade econômica dos sistemas de cultivo com Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby e Ananas comosus var. erectifolius (L. B. Smith) Coppus & Leal, considerando-se três sistemas distintos: I) Monocultivo de Paricá; II) Monocultivo de Curauá; e III) Sistema Paricá e Curauá. Os sistemas foram implantados no Campo Experimental da Empresa Tramontina Belém, localizado no município de Aurora do Pará (PA). A partir dos registros das contas de despesa e receita do orçamento unitário, elaborados para cada sistema, foi construído o fluxo de caixa. A viabilidade econômica foi determinada por meio do valor presente líquido (VPL), razão benefício/custo (B/C) e taxa interna de retorno (TIR). Utilizou-se como custo de oportunidade uma taxa de juros de longo prazo de 12% ao ano. Os custos e as receitas foram mensurados em R$/ha. Os resultados mostraram que o monocultivo de Curauá apresentou o maior VPL (R$ 19.853,44), seguido do sistema agroflorestal de Paricá e Curauá (R$ 9.507,795). O sistema Paricá e Curauá apresentou a maior relação benefício/custo (1,29) enquanto a menor ficou com o monocultivo de Paricá. Das atividades analisadas, o monocultivo de Curauá apresentou maior TIR (44%), seguido do sistema Paricá e Curauá (33%), valores superiores ao custo de oportunidade. A associação Paricá e Curauá mostrou-se economicamente viável, tanto para agricultores que desejam implantar um povoamento florestal, quanto para as empresas madeireiras interessadas na redução dos custos da implantação de povoamentos florestais

The effect of some processing conditions on the characteristics of biodegradable microspheres obtained by an emulsion solvent evaporation process

Unloaded microspheres were prepared from polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHB-HV) polymers using an oil-in-water emulsion solvent evaporation method. The study was conducted to evaluate how the polymer and some process parameters affect properties of the final microspheres such as particle size, superficial area, zeta potential, surface morphology and microsphere degradation. The variables included surfactant concentration in the emulsion water phase and solvent composition. From the results, it was found that the parameters affecting microsphere size the most were surfactant concentration in the emulsion water phase and solvent composition. Properties such as zeta potential, surface area and surface morphology remained pratically unchanged over the range of the processing conditions studied here.011