Ion backflow studies with a triple-GEM stack with increasing hole pitch

Gas Electron Multipliers have undergone a very consistent development since their invention in 1997. Their production procedures have been tuned in such a way that nowadays it is possible to produce foils with areas of the order of the square meter that can operate at a reasonable gain, uniform over large areas and with a good stability in what concerns electrical discharges. For the third run of LHC, they will be included in the CMS and ALICE experiments after significant upgrades of the detectors, confirming that these structures are suitable for very large experiments. In the special case of Time Projection Chambers, the ion backflow and the energy resolution are sensitive issues that must be addressed and the GEM has shown to be able to deal with both of them. In this work, a stack of three GEMs with different pitches has been studied as a possible future approach for ion-backflow suppression to be used in TPCs and other detection concepts. With this approach, an ion backflow of 1 % with an energy resolution of 12 % at 5.9 keV has been achieved with the detector operating in an Ar/CO2 (90/10) mixture at a gain of ~ 2000.Comment: 15 pages, 11 figure

Developing personas and proto personas to enhance the art museum visitor experience

This paper aims to study and think about the use of personas and proto personas on the art museum visitors experience. Its object of study is the educational services of art museums focusing on children and young people up to the age of 18. This is a hybrid study - conceptual and empirical – and exploratory study. It was conducted through a qualitative methodology, constructivist paradigm and design approach. It relies on critical and creative thinking, as well on data collection. Using a total of 36 interviews to teachers/educators and children guardians, divided into 2 distinct phases, and a total of 3 pre-test interviews. This paper allowed to draw five conclusions. First, building personas enables the art museum to understand its audience. Visitor’s needs and objectives can be assessed in a more direct and efficient way by adapting designing strategies. Second, they are the basis for redesigning: the museum space, the visitor's journey and the visitor's experience. Third, personas allow to simulate a visitor model with differentiating profiles. Fourth, proto personas are created through brainstorming about the visitors, allowing to generate tools to start the early planning with a lower budget. Significant costs may be reduced and changes to management practices applied. Fifth, providing insights for the construction of a space for creative expression and nonformal education based on the visual arts aimed at children and young people up to the age of 18. This paper expands the investigation of application of the construction of personas and proto personas in the management of educational services in art museums. The value of this study lies in exploration of the construction of personas and in a learning context Do - Feel - Learn instead of the traditional sequence Learn - Feel - Do.info:eu-repo/semantics/publishedVersio

Symmetry reductions of a particular set of equations of associativity in twodimensional topological field theory

The WDVV equations of associativity arising in twodimensional topological field theory can be represented, in the simplest nontrivial case, by a single third order equation of the Monge-Ampe`re type. By investigating its Lie point symmetries, we reduce it to various nonlinear ordinary differential equations, and we obtain several new explicit solutions.Comment: 10 pages, Latex, to appear in J. Phys. A: Math. Gen. 200