Immigrant parents’ perspectives on their children’s mathematics education

This paper draws on two research studies with similar theoretical backgrounds, in two different settings, Barcelona (Spain) and Tucson (USA). From a sociocultural perspective, the analysis of mathematics education in multilingual and multiethnic classrooms requires us to consider contexts, such as the family context, that have an influence on these classrooms and its participants. We focus on immigrant parents' perspectives on their children's mathematics education and we primarily discuss two topics (1) their experiences with the teaching of mathematics, and (2) the role of language (native language and second language). The two topics are explored with reference to the immigrant student's or their parents' former educational systems (the “before”) and their current educational systems (the “now”). Parents and schools understand educational systems, classroom cultures and students' attainment differently, as influenced by their sociocultural histories and contexts.     

Finding Hamiltonian circuits in quasi-adjoint graphs

This paper is motivated by a method used for DNA sequencing by hybridization presented in [Jacek Blazewicz, Marta Kasprzak, Computational complexity of isothermic DNA sequencing by hybridization, Discrete Appl. Math. 154 (5) (2006) 718–729]. This paper presents a class of digraphs: the quasi-adjoint graphs. This class includes the ones used in the paper cited above. A polynomial recognition algorithm in O(n³), as well as a polynomial algorithm in O(n²+m²) for finding a Hamiltonian circuit in these graphs are given. Furthermore, some results about related problems such as finding a Eulerian circuit while respecting some forbidden transitions (a path with three vertices) are discussed.     

Extrapolation of accelerated thermooxidative tests to lower temperatures applying non-Arrhenius temperature functions

Extrapolations of the accelerated thermooxidative tests, based on the Arrhenius and two non-Arrhenius temperature functions, have been tested for 26 data sets. The data cover a wide range of materials from polyolefins and other polymers to biodiesel, edible oils and dried milk. It has been found that the extrapolation from high-temperature data to ambient temperature based on the Arrhenius temperature function leads to the estimations of unrealistically long durability. The best estimations corresponding most with experience are obtained for the extrapolation based on the temperature function k(T)=A _kexp(DT).     

Event recognition by detrended fluctuation analysis: An application to Teide–Pico Viejo volcanic complex, Tenerife, Spain

In this work we investigate the application of the detrended fluctuation analysis (DFA) to seismic data recorded in the island of Tenerife (Canary Islands, Spain) during the month of July 2004, in a phase of possible unrest of the Teide–Pico Viejo volcanic complex. Tectonic events recorded in the area are recognized and located by the Spanish national agency Instituto Geográfico Nacional (IGN) and their catalogue is the only currently available dataset, whose completeness unfortunately suffers from the strong presence of anthropogenic noise. In this paper we propose the use of DFA to help to automatically identify events. The evaluation of this case study proves DFA to be a promising tool to be used for rapidly screening large seismic datasets and highlighting time windows with the potential presence of discrete events.     

Finite groups with small centralizers of word-values

Given a positive integer m and a group-word w, we consider a finite group G such that $$w(G) ne 1$$ and all centralizers of non-trivial w-values have order at most m. We prove that if $$w=v(x_1^{q_1},dots ,x_k^{q_k})$$, where v is a multilinear commutator word and $$q_1, dots , q_k$$ are p-powers for some prime p, then the order of G is bounded in terms of w and m only. Similar results hold when w is the nth Engel word or the word $$w=[x^n, y_1, dots ,y_k]$$ with $$k ge 1$$.     

The kurzweil construction of an integral in ordered spaces

This paper generalizes the results of papers which deal with the Kurzweil-Henstock construction of an integral in ordered spaces. The definition is given and some limit theorems for the integral of ordered group valued functions defined on a Hausdorff compact topological space T with respect to an ordered group valued measure are proved in this paper.     

Smoothness of the Functional Law Generated by a Nonlinear SPDE

The authors consider a stochastic heat equation in dimension d=1 driven by an additive space time white noise and having a mild nonlinearity.It is proved that the functional law of its solution is absolutely continuous and possesses a smooth density with respect to the functional law of the corresponding linear SPDE.     

The converse Lyapunov’s theorem for ODEs of Carathéodory type

The converse problem of Lyapunov stability for systems of ODEs of Caratheodory type is considered. It is proved that if the right hand side of an ODE satisfies only the Osgood condition, the uniform stability of the origin is sufficient to the existence of a locally Lipschitz continuous Lyapunov function. Actually, the uniform stability is equivalent to the robust stability in this case. Moreover, as an auxiliary result, the generalization of the famous Gronwall-Bellman-Bihari inequality is also proved.     

On the bicriterion – minimal cost/minimal label – spanning tree problem

We address a bicriterion spanning tree problem relevant in some application fields such as telecommunication networks or transportation networks. Each edge is assigned with a cost value and a label (such as a color). The first criterion intends to minimize the total cost of the spanning tree (the summation of its edge costs), while the second intends to get the solution with a minimal number of different labels. Since these criteria, in general, are conflicting criteria we developed an algorithm to generate the set of non-dominated spanning trees. Computational experiments are presented and results discussed.     

Interaction enthalpy of lysozyme with vesicles

Negatively charged vesicles made of non-stoichiometric amounts of sodium dodecylsulfate and cetyltrimethylammonium bromide were characterised by physico-chemical methods. Interactions with lysozyme were examined by calorimetry. A remarkable heat effect is observed upon diluting the protein with the vesicular pseudo-solvent. The maximum ΔH_bind value occurs at complete vesicle charge neutralisation by the protein.