Satisfiability Testing for Boolean Formulas Using Δ-trees

The tree-based data structure of -tree for propositional formulas is introduced in an improved and optimised form. The -trees allow a compact representation for negation normal forms as well as for a number of reduction strategies in order to consider only those occurrences of literals which are relevant for the satisfiability of the input formula. These reduction strategies are divided into two subsets (meaning- and satisfiability-preserving transformations) and can be used to decrease the size of a negation normal form A at (at most) quadratic cost. The reduction strategies are aimed at decreasing the number of required branchings and, therefore, these strategies allow to limit the size of the search space for the SAT problem.     

Geometric orientation by humans: angles weigh in

Human participants were trained to navigate to two geometrically equivalent corners of a parallelogram-shaped virtual environment. The unique shape of the environment combined three distinct types of geometric information that could be used in combination or in isolation to orient and locate the goals: the angular amplitudes of the corners, the relative wall length relationships, and the principal axis of symmetry. In testing, participants were placed in manipulated versions of the training environment that tested which types of geometry they had encoded and how angular information weighed in against the other two geometric properties. The test environments were (a) a rectangular environment that removed the angular information, (b) a rhombic environment that removed wall length information and drastically reduced the principal axis, and (c) a reverse-parallelogram-shaped environment that placed angular information against both wall length and principal axis information. Participants chose accurately in the rectangular and rhombus environments, despite the removal of one of the cues. In the conflict test, participants preferred corners with the correct angular amplitudes over corners that were correct according to both wall length relationships and the principal axis. These results are comparable to recent findings with pigeons and suggest that angles are a salient orientation cue for humans.     

Water Access and Subjective Well-Being: The Case of Sucre,Bolivia

In this paper we study the influence of residential water access on subjective well-being. The data come from original field work that includes 535 households in Sucre, Bolivia, a city with deficits in the water service. We relate two subjective well-being measures, satisfaction with life and satisfaction with the water domain, to water access variables. It could be the case that the effect of water access variables in subjective well-being could be spurious. That is, water access variables could be capturing shortfalls in other basic needs, such as a lack of income. In order to avoid spurious conclusions, we include socioeconomic variables such as income and place of residence in the regression as control variables. In addition, people might adapt to having poor access to water. The significance of the coefficients of the water variables could lead us to conclude that people do not adapt, but non significance means we cannot reject this possibility. In the econometric regressions, water variables such as water cuts, water quality and access quality, when added to the control variables, increase goodness-to-fit affecting both subjective well-being measures. Our results permit to assess the importance of key elements of access to water in the region under study by relating them to subjective well-being and reveal that water access influences subjective well-being beyond adaptation and other socioeconomic characteristics. Taking this into consideration, we propose that well-being studies in developing countries should consider water access aspects.     

Why do adolescents use drugs? A common sense explanatory model from the social actor's perspective

Analysis was made of the common sense explanations of 60 Mexican teenage illicit drug users in rehabilitation to determine their drug use debut. The explanatory model was separated into three blocks, two of which contained common sense aspects: interaction between subject's plane and the collectivity; and relationship between subject's interior (subject-family) and exterior (environment or group-pressure). Based on these data, we propose that drug use debut may be linked to subjects' emotional vulnerability which originates in the family image and renders them more susceptible to the influence of others. This kind of reasoning points to a more passive than active, and more social than personal dynamic in drug use debut, important factors for developing preventative measures.     

The effect of interethnic ideologies on the likability of stereotypic vs. counterstereotypic minority targets

This paper examines the effect of interethnic ideologies on the likability of stereotypic vs. counterstereotypic minority targets. In two experiments, participants were exposed to either a multicultural or colorblind prime and subsequently asked to indicate their impressions of a stereotypic or counterstereotypic minority target. Results suggest that multiculturalism and colorblindness have different effects on the likability of minority targets to the extent that such targets confirm the existence of fixed or permeable ethnic group boundaries. Specifically, a stereotypic target was liked more than a counterstereotypic target when participants were exposed to multiculturalism - suggesting that multiculturalism creates a preference for individuals who remain within the boundaries of their ethnicity. Conversely, a counterstereotypic target was liked more than a stereotypic target when participants were exposed to colorblindness - suggesting that colorblindness creates a preference for individuals who permeate the boundaries of their ethnicity. Theoretical and practical implications are discussed.     

Predictors of quality of life enjoyment and satisfaction in individuals living with HIV and AIDS in a resource-constrained setting in South Africa

The burden of HIV disease is concentrated in sub-Saharan Africa, particularly in South Africa (SA). Whilst there have been many studies conducted on the biomedical and socio-psychological aspects of HIV and AIDS, insufficient attention has been paid to the quality of life of those infected with the virus. The primary purpose of the study was to determine the predictors of quality of life enjoyment and satisfaction (Q-LES) among individuals infected with HIV. A battery of questionnaires, which included the Hospital Anxiety and Depression Scale (HADS) and the Quality of Life Enjoyment and Satisfaction Questionnaire (Q-LES-Q), were administered to 121 participants. Data was analysed using SPSS. Of the total sample (n = 121), 74% were females. The study found that a large proportion (49.5%) of the sample within the age group 25–49 years old experienced psychological distress. Those who were not on antiretroviral treatment (ART) were significantly affected (66%). Psychological distress was significantly prevalent among HIV positive individuals and also the strongest predictor of Q-LES among these individuals.     

Letter transpositions within and across morphemic boundaries: Is there a cross-language difference?

Research on the impact of letter transpositions that arise across morpheme boundaries has yielded conflicting results. These results have led to the suggestion that a cross-linguistic difference may exist in the recognition of Spanish and English words. In two masked-priming experiments run on separate groups of Spanish and English speakers, we tested this hypothesis by comparing the impacts of primes with letter transpositions that arose within morphemes or across morpheme boundaries on the recognition of identical or near-identical Spanish–English cognate targets. The results showed transposed-letter benefits in both Spanish and English that were not modulated by the position of the transposed letter in the prime stimulus. Our findings therefore add to the growing body of literature suggesting that the transposed-letter benefit is not affected by the position of the transposed letters relative to the morpheme boundary, and they dispel previous suggestions that there might be a genuine difference in orthographic coding across the Spanish and English writing systems.     

Some Thoughts on A. H. Louie’s “More Than Life Itself: A Reflection on Formal Systems and Biology”

We review and discuss A. H. Louie’s book “More than Life Itself: A Reflexion on Formal Systems and Biology” from an interdisciplinary viewpoint, involving both biology and mathematics, taking into account new developments and related theories.     

Application of Hellison's Teaching Personal and Social Responsibility Model in physical education to improve self-efficacy for adolescents at risk of dropping-out of school

This study evaluated improvement in self-efficacy and personal and social responsibility among at-risk of dropping-out of school adolescents participating in a program in which Hellison's Teaching Personal and Social Responsibility Model was applied in physical education classes during the course of an academic year. Thirty at-risk adolescents aged 13-14 years old (23 boys, 7 girls) were assigned to an intervention group (12 boys and 3 girls) or a comparison group (11 boys, 4 girls), the latter of which did not participate in the program. Quantitative results showed a significant improvement in the students' self-efficacy for enlisting social resources and in self-efficacy for self-regulated learning. Qualitative results showed an improvement in responsibility behaviors of participants in the intervention group. This suggests that the model could be effective for improving psychological and social development in at-risk adolescents, and that physical education classes may be an appropriate arena for working with these young people.     

Absence of effect of the change of food context in the activity-based anorexia phenomenon in rats

The goal of this study was to analyse how the context in which animals remain during the period of access to food modulates the development of activity-based anorexia in rats. For this purpose, the effect of changing the context of the activity period and the eating period was measured in terms of body weight loss, reduction in food intake and increase in physical activity. A 2 yen 2 factorial design was implemented, by having or not having access to a running wheel, and by being exposed or not exposed to a context change. Results showed that exposure to different contexts for the wheel and for the food did not affect weight loss, food intake or activity levels. These results are in line with the theoretical position of Epling and Pierce (1992) that activity is induced by the food restriction regime.