Efficient data structures for backtrack search SAT solvers

The implementation of efficient Propositional Satisfiability (SAT) solvers entails the utilization of highly efficient data structures, as illustrated by most of the recent state-of-the-art SAT solvers. However, it is in general hard to compare existing data structures, since different solvers are often characterized by fairly different algorithmic organizations and techniques, and by different search strategies and heuristics. This paper aims the evaluation of data structures for backtrack search SAT solvers, under a common unbiased SAT framework. In addition, advantages and drawbacks of each existing data structure are identified. Finally, new data structures are proposed, that are competitive with the most efficient data structures currently available, and that may be preferable for the next generation SAT solvers

Boosting Haplotype Inference with Local Search

Abstract. A very challenging problem in the genetics domain is to infer haplotypes from genotypes. This process is expected to identify genes affecting health, disease and response to drugs. One of the approaches to haplotype inference aims to minimise the number of different haplotypes used, and is known as haplotype inference by pure parsimony (HIPP). The HIPP problem is computationally difficult, being NP-hard. Recently, a SAT-based method (SHIPs) has been proposed to solve the HIPP problem. This method iteratively considers an increasing number of haplotypes, starting from an initial lower bound. Hence, one important aspect of SHIPs is the lower bounding procedure, which reduces the number of iterations of the basic algorithm, and also indirectly simplifies the resulting SAT model. This paper describes the use of local search to improve existing lower bounding procedures. The new lower bounding procedure is guaranteed to be as tight as the existing procedures. In practice the new procedure is in most cases considerably tighter, allowing significant improvement of performance on challenging problem instances.

Acantholippia salsoloides : Phytochemical Composition and Biological Potential of a Thujonic Population

Acantholippia salsoloides (Verbenaceae) is an aromatic plant widespread in the Andean region. The infusion (leaves and flowers) is widely used as a digestive stimulant as well as for the treatment of various diseases in traditional medicine. A. salsoloides attributes its common name “rica-rica” to the fresh and sweet fragrance of the plant. In this work, 2 different polar extracts and the essential oil of a selected rica-rica population were studied. The phenolic composition was analyzed by high-performance liquid chromatography diode array detector; the essential oil profile was determined by gas-chromatography ion-trap mass spectrometry/flame ionization detection. For all extracts, the antibacterial potential was performed by in vitro assays; the antioxidant and α-glucosidase inhibition were determined in decoction and hydroethanolic extracts. The volatile profile allowed the identification of 26 volatile compounds, β-thujone (84%) being the major one in this rica-rica population. Eighteen phenolic compounds were identified; isoferulic acid (16%-18%) and cynaroside (45%-47%) were the larger ones. In a general way, the hydroethanolic extract was more active against Staphylococcus aureus and Micrococcus luteus (minimum inhibitory concentrations= 0.3- 1.3 mg/mL). Both polar extracts have strong antiradical activities although decoction extract proved to be more active against DPPH· (half-maximal inhibitory concentration [IC50] =36 µg/mL) and O2•− (IC50 =28 µg/mL) while hydroethanolic extract shows higher action over α-glucosidase (IC50 =217 µg/mL). The results suggest that A. salsoloides leaves and flowers may be an interesting source of natural antioxidants, antidiabetics, or antimicrobials, and could be used in dietary supplements, medicinal products and pharmaceutical formulations.Fil: Celaya, Liliana Soledad. Universidad Nacional de Jujuy. Centro Interdisciplinario de Investigaciones En Tecnologias y Desarrollo Social Para El Noa. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Saltajujuy. Centro Interdisciplinario de Investigaciones En Tecnologias y Desarrollo Social Para El Noa.; Argentina. Universidad Nacional de Misiones; ArgentinaFil: Viturro, Carmen Ines. Universidad Nacional de Jujuy. Centro Interdisciplinario de Investigaciones En Tecnologias y Desarrollo Social Para El Noa. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Saltajujuy. Centro Interdisciplinario de Investigaciones En Tecnologias y Desarrollo Social Para El Noa.; Argentina. Universidad Nacional de Jujuy; ArgentinaFil: Silva, Luís R.. Universidade da Beira Interior; Portuga

Efficient Haplotype Inference with Pseudo-Boolean Optimization

Abstract. Haplotype inference from genotype data is a key computational problem in bioinformatics, since retrieving directly haplotype information from DNA samples is not feasible using existing technology. One of the methods for solving this problem uses the pure parsimony criterion, an approach known as Haplotype Inference by Pure Parsimony (HIPP). Initial work in this area was based on a number of different Integer Linear Programming (ILP) models and branch and bound algorithms. Recent work has shown that the utilization of a Boolean Satisfiability (SAT) formulation and state of the art SAT solvers represents the most efficient approach for solving the HIPP problem. Motivated by the promising results obtained using SAT techniques, this paper investigates the utilization of modern Pseudo-Boolean Optimization (PBO) algorithms for solving the HIPP problem. The paper starts by applying PBO to existing ILP models. The results are promising, and motivate the development of a new PBO model (RPoly) for the HIPP problem, which has a compact representation and eliminates key symmetries. Experimental results indicate that RPoly outperforms the SAT-based approach on most problem instances, being, in general, significantly more efficient

Secure webs and buying intention: the moderating role of usability

El presente trabajo ha planteado un modelo conceptual a fin de mostrar como los antecedentes de la intención de compra se ven reforzados en contextos de Webs altamente usables. Específicamente, el trabajo analiza en profundidad el rol moderador de la usabilidad en la explicación de la conexión entre seguridad de una Web e intención de compra. Entre ambos extremos (seguridad e intención de compra), se han incluido diversas variables para explicar mejor su conexión. Para ello, ha sido diseñada una Web ficticia de ropa dirigida al segmento joven de clase media. A fin de alterar la usabilidad de la Web se han realizado dos tipos de manipulaciones: la velocidad y la facilidad de uso de la Web. Las dos Webs creadas (alta usabilidad y baja usabilidad) fueron visitadas por un total de 170 encuestados que fueron compensados con un USB valorado en 15 euros. Los resultados muestran que la seguridad percibida en la Web acarrea tres interesantes efectos (especialmente para la Web altamente usable): (i) mejora las actitudes agrado, (ii) reduce el nivel de riesgo percibido; (iii) aumenta la confianza. Los dos últimos efectos, a su vez, acaban aumentando la intención de compra.. Por último, se ha demostrado que la usabilidad, efectivamente, refuerza las relaciones consideradas en el modelo propuesto para explicar la intención de compra.A conceptual model has been proposed to show how buying intention antecedents are reinforced in highly usable contexts. Specifically, this paper deeply analyses the moderator role of system variables (usability) on explaining the relationship between Web security and buying intention. Between both extremes (security and buying intention), several relationships have also been stated to better explain this effect. An “ideal” fictitious Website was designed for a non existent clothing company directed at the segment of middle class consumers. In order to alter Web usability, two blocks of changes were made, one concerning Website speed and the other related to ease of use. Our experiment sample consisted of 170 respondents who participated in exchange for a pen-drive (USB) valued at 15 euros. The results show that improving website security has three interesting effects (especially in high usable contexts): (i) it improves pleasure attitudes, (ii) reduces the level of perceived risk and (iii) increases trust. Secondly, it has been found that to increase buying intention, two actions must be taken: (i) to diminish perceived risk and (ii) to improve users’ pleasure attitudes towards the Website. Finally, usability has been found to have a moderating role in all the relationships considered (reinforcing them)

Modelling and analysis of forest fire data in Portugal

In the last decade, forest fires have become a natural disaster in Portugal, causing great forest devastation, leading to both economic and environmental losses and putting at risk populations and the livelihoods of the forest itself. In this work, we present Bayesian hierarchical models to analyze spatio-temporal fire data on the proportion of burned area in Portugal, by municipalities and over three decades. Mixture of distributions was employed to model jointly the proportion of area burned and the excess of no burned area for early years. For getting estimates of the model parameters, we used Monte Carlo Markov chain methods

The Discoursive Construction of Sexuality and Domesticity in the Brazilian 1950s

This thesis analyses models and messages of femininity in the Brazilian 1950s, as expressed in popular culture in general and by normative literature destined for women readers. These sources indicate ways in which post-war Brazilian society attempted to accommodate the appeal of new models and values as displayed in films and magazines to the traditional ethics. Conversely they also represent a discursive site in which attempts to reconcile the restrictions of that ethics with the exigencies of modern bourgeois society were negotiated. First it deals with the foundations of the construction of femininity in Brazilian middle class terms discussing the gendered nature of Catholic doctrine and examining the cultural complex of honour and shame which informs traditional position of women in society. These patterns were transmitted by normative literature and reinforced through romantic novels. The analysis of the process of courtship ('namoro') and the description of the desacralization of woman in cartoons and pornographic comics reveal much about male values. 'Namoro' was embedded with ideas of chivalry derived from courtly love which awarded woman a high and sacred position. It is sharply contrasted with representations of women in male popular fiction. Images of woman in popular culture were frequently opposed to traditional representations which centred on modesty and passivity, and which either sanctified sexuality (in wedlock), or saw it as transgressive (outside the sphere of family). The new genre of advertisements, however, heightened sexual allure as the necessary element of femininity, contributing to 'domestication of seduction'. The counterpart of this seductive woman, was the new efficient housewife and mother, the target consumer of domestic appliances. Although at first glance it seems that imagery of consumption embodied the old dichotomy between the good asexual woman/mother/Mary/ and the bad/sexy /Eve/source of illicit pleasures, it will be argued that both are facets of the same ambiguous figure. Those models were pivotal for establishing parameters for the self-evaluation of middle-class women. They were also important for the construction of new paradigms for Brazilian society. A society which was trying to adjust its own image to that of a new world where progress, modernisation and democracy were seen as global ideals