From Wrapping to Knowledge

One the most challenging problems for enterprise information integration is to deal with heterogeneous information sources on the Web. The reason is that they usually provide information that is in human-readable form only, which makes it difficult for a software agent to understand it. Current solutions build on the idea of annotating the information with semantics. If the information is unstructured, proposals such as S-CREAM, MnM, or Armadillo may be effective enough since they rely on using natural language processing techniques; furthermore, their accuracy can be improved by using redundant information on the Web, as C-PANKOW has proved recently. If the information is structured and closely related to a back-end database, deep annotation ranges among the most effective proposals, but it requires the information providers to modify their applications; if deep annotation is not applicable, the easiest solution consists of using a wrapper and transforming its output into annotations. In this paper, we prove that this transformation can be automated by means of an efficient, domain-independent algorithm. To the best of our knowledge, this is the first attempt to devise and formalize such a systematic, general solution     

Optimum modulation and demodulation matrices for solar polarimetry

Both temporal and/or spatial modulation are mandatory in current solar polarimetry [Appl. Opt. 24, 3893 (1985); 26, 3838 (1987)]. The modulating and demodulating processes are mathematically described by matrices O and D, respectively, on whose structure the accuracy of Stokes parameter measurements depend. We demonstrate, based on the definition of polarimetric efficiency [Instituto de Astrofísica de Canarias Internal Report (1994); ASP Conf. Ser. 184, 3 (1999)], that the maximum efficiencies of an ideal polarimeter are unity for Stokes I and for (Q(2) + U(2) + V(2))(1/2) and that this occurs if and only if O(T)O is diagonal; given a general (possibly nonideal) modulation matrix O, the optimum demodulation matrix turns out to be D = (O(T)O)(-1)O(T); and the maximum efficiencies in the nonideal case are given by the rms value of the column elements of matrix O and are reached by modulation matrices such that O(T)O is diagonal. From these analytical results we distill two recipes useful in the practical design of polarimeters. Their usefulness is illustrated by discussing cases of currently available solar polarimeters. Although specifically devoted to solar polarimetry, the results here may be applied in practically all other branches of science for which polarimetric measurements are needed.     

Evaluating Bayesian networks’ precision for detecting students’ learning styles

Students are characterized by different learning styles, focusing on different types of information and processing this information in different ways. One of the desirable characteristics of a Web-based education system is that all the students can learn despite their different learning styles. To achieve this goal we have to detect how students learn: reflecting or acting; steadily or in fits and starts; intuitively or sensitively. In this work, we evaluate Bayesian networks at detecting the learning style of a student in a Web-based education system. The Bayesian network models different aspects of a student behavior while he/she works with this system. Then, it infers his/her learning styles according to the modeled behaviors. The proposed Bayesian model was evaluated in the context of an Artificial Intelligence Web-based course. The results obtained are promising as regards the detection of students’ learning styles. Different levels of precision were found for the different dimensions or aspects of a learning style.     

Phase Behavior and Structure of Systems Based on Mixtures of n‐Hentriacontane and Melissic Acid

Candelilla wax (CW) organogelation is a promising method for providing structure to solid‐like fat‐based foods, cosmetics, and drug delivery systems. The main component, n‐hentriacontane (C31), defines, to a large extent, the thermal properties of CW. CW is a complex mixture of n‐alkanes, fatty acids, triterpenic alcohols, and fatty alcohols. In this initial examination of the role of CW components on the phase behavior and structure, CW and binary mixtures of C31 and melissic acid (C30) were studied in bulk and in solutions of vegetable oil. Binary mixtures of C31 and C30 presented a predominantly monotectic phase behavior in which the melting temperature of C31 remained constant independently of the mixture composition. Crystal packing of the pure components and mixtures had an orthorhombic subcell, and the microstructures of the mixtures were extremely different from that of the pure components. In solutions with less than 50 % C31, the order–disorder transition observed in bulk C31 was absent. Organogels of C31, C30, or the mixture were softer than those of CW. The increased strength of CW organogels is associated with the relatively small crystal size of this system.     

Fluorescence from the maillard reaction and its potential applications in food science

The chemistry of the Maillard reaction involves a complex set of steps, and its interpretation represents a challenge in basic and applied aspects of Food Science. Fluorescent compounds have been recognized as important early markers of the reaction in food products since 1942. However, the recent advances in the characterization of fluorophores' development were observed in biological and biomedical areas. The in vivo non-enzymatic glycosylation of proteins produces biological effects, promoting health deterioration. The characteristic fluorescence of advanced glycosylation end products (AGEs) is similar to that of Maillard food products and represents an indicator of the level of AGE-modified proteins, but the structure of the fluorescent groups is, typically, unknown. Application of fluorescence measurement is considered a potential tool for addressing key problems of food deterioration as an early marker or index of the damage of biomolecules. Fluorophores may be precursors of the brown pigments and/or end products. A general scheme of the Maillard reaction is proposed in this article, incorporating the pool concept. A correct interpretation of the effect of environmental and compositional conditions and their influences on the reaction kinetics may help to define the meaning of fluorescence development for each particular system.     

Iron(II)-catalyzed oxidation of arsenic(III) in a sediment column

Arsenic contamination in aquatic systems is a worldwide concern. Understanding the redox cycling of arsenic in sediments is critical in evaluating the fate of arsenic in aquatic environments and in developing sediment quality guidelines. The direct oxidation of inorganic trivalent arsenic, As(III), by dissolved molecular oxygen has been studied and found to be quite slow. A chemical pathway for As(III) oxidation has been proposed recently in which a radical species, Fe(IV), produced during the oxidation of divalent iron, Fe(II), facilitates the oxidation of As(III). Rapid oxidation of As(III) was observed (on a time scale of hours) in batch systems at pH 7 and 7.5, but the extent of As(III) oxidation was limited. The Fe(II)-catalyzed oxidation of As(III) is examined in a sediment column using both computational and experimental studies. A reactive-transport model is constructed that incorporates the complex kinetics of radical species generation and Fe(II) and As(III) oxidation that have been developed previously. The model is applied to experimental column data. Results indicate that the proposed chemical pathway can explain As(III) oxidation in sediments and that transport in sediments plays a vital role in increasing the extent of As(III) oxidation and efficiency of the Fe(II) catalysis.