Ordinary differential equations and descriptive set theory: uniqueness and globality of solutions of Cauchy problems in one dimension

We study some natural sets arising in the theory of ordinary differential equations in one variable from the point of view of descriptive set theory and in particular classify them within the Borel hierarchy. We prove that the set of Cauchy problems for ordinary differential equations which have a unique solution is $\Pi^0_2$-complete and that the set of Cauchy problems which locally have a unique solution is $\Sigma^0_3$-complete. We prove that the set of Cauchy problems which have a global solution is $\Sigma^0_4$-complete and that the set of ordinary differential equation which have a global solution for every initial condition is $\Pi^0_3$-complete. We prove that the set of Cauchy problems for which both uniqueness and globality hold is $\Pi^0_2$-complete

Developing independent learning skills via the web

This poster presentation examines the impact of the web-based resources produced to develop information literacy and research skills required to complete the dissertation module for a BSc in Information Management. This module was selected because of its emphasis on independent learning, and web resources were designed to provide a support framework that would enable students to operate as effective independent learners. Preliminary findings have shown that students at the advanced level of the degree are not equipped with independent learning skills and are particularly poor at the types of competences promoted by the Society of College, National and University Libraries (SCONUL)’s Information Skills model. We will assess the effectiveness of the web-based resources to develop these skills by examining student and peer-based feedback

Solving Irregular Strip Packing Problems With Free Rotations Using Separation Lines

Solving nesting problems or irregular strip packing problems is to position polygons in a fixed width and unlimited length strip, obeying polygon integrity containment constraints and non-overlapping constraints, in order to minimize the used length of the strip. To ensure non-overlapping, we used separation lines. A straight line is a separation line if given two polygons, all vertices of one of the polygons are on one side of the line or on the line, and all vertices of the other polygon are on the other side of the line or on the line. Since we are considering free rotations of the polygons and separation lines, the mathematical model of the studied problem is nonlinear. Therefore, we use the nonlinear programming solver IPOPT (an algorithm of interior points type), which is part of COIN-OR. Computational tests were run using established benchmark instances and the results were compared with the ones obtained with other methodologies in the literature that use free rotation

Information literacy education in the UK: reflections on perspectives and practical approaches of curricular integration

This paper has two main aims, to present the current position of information literacy education in UK-based academic institutions and to propose a strategy that ensures the integration of this phenomenon in learning and teaching institutional practices. The first part of the paper offers an insight into the perceptions of information literacy by exploring four distinct perspectives, including the institutional angle and the views associated with faculty staff, library staff and students. What transpires from the findings is that information literacy from an institutional perspective is dominated by the need to measure information skills within the context of information as a discipline in its own right. Another issue that is raised by the data points to a great deal of misinformation regarding information literacy, and that, as a result, a clear marketing strategy must be adopted by information professionals to address the misconceptions held by faculty staff and students alike. We aim to address these points by drawing on recent scholarship and research in the field which demonstrates the validity of information literacy as a process for fostering independent learning. The second part of the paper explains how a Fellowship project has placed information literacy on the pedagogical agenda of the University of Staffordshire in the UK by promoting information literacy education as an integrated element of the curriculum

The EUV spectrum of the Sun: SOHO CDS NIS radiances during solar cycle 23

For the first time, we present and discuss EUV radiances of the solar transition region (TR) and corona obtained during a solar cycle. The measurements were obtained with the SOHO/coronal diagnostic spectrometer (CDS) during the period from 1996 to 2010. We find that limb-brightening significantly affects any characterisation of the solar radiances. We present the limb-brightening function for the main lines and find that it does not change measurably during the cycle. We confirm earlier findings that the radiance histogram of the cooler lines have a well defined, log-normal quiet-Sun component, although our results differ from previous ones. The width of the lowest-radiance log-normal distribution is constant along the cycle. Both the analysis of the centre-to-limb variation and of the radiance statistical distribution point to a constant QS emission along solar cycle 23. Lines formed above 1 MK are dramatically affected by the presence of active regions, and indeed, no "quiet Sun" region can be defined during periods of maximum activity. Much of the irradiance variability in lines formed below 1.5 MK is due to a change in the emitting area. For hotter lines, the emitting area saturates to almost 100% of full solar disk at the maximum of activity, while simultaneously the emission due to active regions increases by more than an order of magnitude. We show that structures around active regions, sometimes referred to as dark halos or dark canopies, are common and discuss their similarities and differences with coronal holes. In particular, we show how they are well visible in TR lines, contrary to coronal holes.Comment: 15 pages, 11 figures, 2 tables; in press in: Astronomy & Astrophysic

Modelling solar low-lying cool loops with optically thick radiative losses

We investigate the increase of the DEM (differential emission measure) towards the chromosphere due to small and cool magnetic loops (height $\lesssim8$~Mm, $T\lesssim10^5$~K). In a previous paper we analysed the conditions of existence and stability of these loops through hydrodynamic simulations, focusing on their dependence on the details of the optically thin radiative loss function used. In this paper, we extend those hydrodynamic simulations to verify if this class of loops exists and it is stable when using an optically thick radiative loss function. We study two cases: constant background heating and a heating depending on the density. The contribution to the transition region EUV output of these loops is also calculated and presented. We find that stable, quasi-static cool loops can be obtained by using an optically thick radiative loss function and a background heating depending on the density. The DEMs of these loops, however, fail to reproduce the observed DEM for temperatures between $4.6<\log T<4.8$. We also show the transient phase of a dynamic loop obtained by considering constant heating rate and find that its average DEM, interpreted as a set of evolving dynamic loops, reproduces quite well the observed DEM.Comment: Accepted for publication in A&A on Aug 21st 2015. arXiv admin note: text overlap with arXiv:1112.030

Italy seen through British eyes: a European middle power?

This article analyses the British perceptions of contemporary Italy and Italian politics. Through the use of a number of sources (parliamentary debates, governmental documents, newspaper articles and interviews) it argues that Italy is not perceived, within Great Britain, as a great power within the European system nor it is viewed as a peripheral actor. Rather, it suggests that Italy seems to have finally found in the post-Cold War scenario its proper role–a European middle power, with important responsibilities within a regional sub-system. A frequent request–and expectation–coming from British politics and society is that Italy should take on more international responsibilities, even in the sphere of defence–as the different readings of Italy's role and leadership in Afghanistan and Lebanon reveal. However, Italy's ability to play this role is believed to be hampered by several factors: its uncertain political situation, its unwillingness to engage in military operations, its reluctance to respect international commitments and its structural economic problems. As a result, further possibilities of cooperation with other international partners as well as its potential for autonomous action on the international stage are, in several cases, precluded. Moreover, if the relations between Italy and the UK are usually seen in a positive way, and Italy is viewed as a reliable partner, the nature of the cooperation between the two countries is often considered to be fragile and based on short-term common interests and strategies

Habilidades sociais como fatores de risco e proteção entre homens usuários de crack

As habilidades sociais (HS) são consideradas fatores de risco e de proteção para o consumo de diversas substâncias, porém, essa relação ainda é pouco explorada tratando-se do uso do crack. Assim, objetivou-se avaliar a relação preditiva das HS e das características sociodemográficas sobre o transtorno por uso de crack em 113 homens divididos em dois grupos: usuários de crack (US) e não usuários de substâncias (NUS). Os instrumentos utilizados foram: entrevista de características sociodemográficas e o Inventário de Habilidades Sociais. Os resultados identificaram que maiores habilidades sobre enfrentamento com risco (OR=8,6) e menores habilidades de conversação e desenvoltura social (OR=-0,19) apresentaram-se como fatores de risco para pertencer aos US. Ter filhos (OR=4,9) e ser solteiro (OR=9,6) ou separado/divorciado (OR=7,3), também aumentou a probabilidade do uso do crack. Enfatiza-se a importância de incluir, nos programas de prevenção primária ao transtorno por uso do crack, aspectos das HS específicas e questões relacionadas ao contexto familiar.The social skills (SS) are considered risk factors and protection for the use of various substances, however, this relationship still is not explored in the case of crack use. It aimed to evaluate the predictive relationship of SS and sociodemographic characteristics of the crack use disorder in 113 men divided into two groups: crack users (CU) and non-users of substances (NUS). The instruments used were: sociodemographic characteristics interview and the Social Skills Inventory. The results showed that higher skills for coping with risk (OR=8,6) and lower conversational skills and social resourcefulness (OR=-0,19) were presented as risk factors to belong to crack CU. Having children (OR=4,9) and being single (OR=9,6) or separated / divorced (OR=7,3), also has increased the likelihood of CU. It should be emphasized the importance of including, in the primary prevention programs for crack use disorder, specific aspects of the SS and issues related to the family context