Showing papers by "University of Córdoba (Spain) published in 2008"
15 Oct 2008
TL;DR: KEEL as discussed by the authors is a software tool to assess evolutionary algorithms for data mining problems of various kinds including regression, classification, unsupervised learning, etc., which includes evolutionary learning algorithms based on different approaches: Pittsburgh, Michigan and IRL.
Abstract: This paper introduces a software tool named KEEL which is a software tool to assess evolutionary algorithms for Data Mining problems of various kinds including as regression, classification, unsupervised learning, etc. It includes evolutionary learning algorithms based on different approaches: Pittsburgh, Michigan and IRL, as well as the integration of evolutionary learning techniques with different pre-processing techniques, allowing it to perform a complete analysis of any learning model in comparison to existing software tools. Moreover, KEEL has been designed with a double goal: research and educational.
1,297 citations
TL;DR: This work describes the full process for mining e-learning data step by step as well as how to apply the main data mining techniques used, such as statistics, visualization, classification, clustering and association rule mining of Moodle data.
Abstract: Educational data mining is an emerging discipline, concerned with developing methods for exploring the unique types of data that come from the educational context. This work is a survey of the specific application of data mining in learning management systems and a case study tutorial with the Moodle system. Our objective is to introduce it both theoretically and practically to all users interested in this new research area, and in particular to online instructors and e-learning administrators. We describe the full process for mining e-learning data step by step as well as how to apply the main data mining techniques used, such as statistics, visualization, classification, clustering and association rule mining of Moodle data. We have used free data mining tools so that any user can immediately begin to apply data mining without having to purchase a commercial tool or program a specific personalized tool.
1,049 citations
TL;DR: In this paper, the authors provide a brief overview of the complex biofuel issue, providing the latest update of the production and potential of biofuels in the transport sector including types of biofuel, feedstocks and technologies and some of the possible socioeconomic, environmental and political implications of the widespread use of bio fuels in our society.
Abstract: Environmental issues, the growing demand for energy, political concerns and the medium-term depletion of petroleum has created the need for development of sustainable technologies based on renewable raw materials. Biofuels might help to meet the future energy supply demands as well as contributing to a reduction of green house gas emissions. Although this topic is highly controversial and many investigations are currently ongoing, this review is intended to give a brief overview about certain aspects of the complex biofuel issue, providing the latest update of the production and potential of biofuels in the transport sector including types of biofuel, feedstocks and technologies and some of the possible socio-economic, environmental and political implications of the widespread use of biofuels in our society.
542 citations
TL;DR: It has been found that it is necessary a previous methanol removal to avoid the saturation of the adsorbents in post transesterification purification.
367 citations
Proceedings Article•
20 Jun 2008TL;DR: It is claimed that a classifier model appropriate for educational use has to be both accurate and comprehensible for instructors in order to be of use for decision making.
Abstract: In this paper we compare different data mining methods and techniques for classifying students based on their Moodle usage data and the final marks obtained in their respective courses. We have developed a specific mining tool for making the configuration and execution of data mining techniques easier for instructors. We have used real data from seven Moodle courses with Cordoba University students. We have also applied discretization and rebalance preprocessing techniques on the original numerical data in order to verify if better classifier models are obtained. Finally, we claim that a classifier model appropriate for educational use has to be both accurate and comprehensible for instructors in order to be of use for decision making.
361 citations
TL;DR: It seems that nitroreductase genes may be controlled by the MarRA and SoxRS regulatory systems that are involved in responses to several antibiotics and environmental chemical hazards and to specific oxidative stress conditions.
Abstract: Most nitroaromatic compounds are toxic and mutagenic for living organisms, but some microorganisms have developed oxidative or reductive pathways to degrade or transform these compounds. Reductive pathways are based either on the reduction of the aromatic ring by hydride additions or on the reduction of the nitro groups to hydroxylamino and/or amino derivatives. Bacterial nitroreductases are flavoenzymes that catalyze the NAD(P)H-dependent reduction of the nitro groups on nitroaromatic and nitroheterocyclic compounds. Nitroreductases have raised a great interest due to their potential applications in bioremediation, biocatalysis, and biomedicine, especially in prodrug activation for chemotherapeutic cancer treatments. Different bacterial nitroreductases have been purified and their biochemical and kinetic parameters have been determined. The crystal structure of some nitroreductases have also been solved. However, the physiological role(s) of these enzymes remains unclear. Nitroreductase genes are widely spread within bacterial genomes, but are also found in archaea and some eukaryotic species. Although studies on regulation of nitroreductase gene expression are scarce, it seems that nitroreductase genes may be controlled by the MarRA and SoxRS regulatory systems that are involved in responses to several antibiotics and environmental chemical hazards and to specific oxidative stress conditions. This review covers the microbial distribution, types, biochemical properties, structure and regulation of the bacterial nitroreductases. The possible physiological functions and the biotechnological applications of these enzymes are also discussed.
355 citations
TL;DR: It is shown that the supramolecular network and the SAM can both be deposited from solution, which should enable the widespread and flexible use of this combined fabrication method, and can be combined to create integrated network–SAM hybrid systems that are sufficiently robust for further processing.
Abstract: One of the central challenges in nanotechnology is the development of flexible and efficient methods for creating ordered structures with nanometre precision over an extended length scale. Supramolecular self-assembly on surfaces offers attractive features in this regard: it is a 'bottom-up' approach and thus allows the simple and rapid creation of surface assemblies, which are readily tuned through the choice of molecular building blocks used and stabilized by hydrogen bonding, van der Waals interactions, pi-pi bonding or metal coordination between the blocks. Assemblies in the form of two-dimensional open networks are of particular interest for possible applications because well-defined pores can be used for the precise localization and confinement of guest entities such as molecules or clusters, which can add functionality to the supramolecular network. Another widely used method for producing surface structures involves self-assembled monolayers (SAMs), which have introduced unprecedented flexibility in our ability to tailor interfaces and generate patterned surfaces. But SAMs are part of a top-down technology that is limited in terms of the spatial resolution that can be achieved. We therefore rationalized that a particularly powerful fabrication platform might be realized by combining non-covalent self-assembly of porous networks and SAMs, with the former providing nanometre-scale precision and the latter allowing versatile functionalization. Here we show that the two strategies can indeed be combined to create integrated network-SAM hybrid systems that are sufficiently robust for further processing. We show that the supramolecular network and the SAM can both be deposited from solution, which should enable the widespread and flexible use of this combined fabrication method.
350 citations
TL;DR: Novel aspects of kisspeptin/GPR54 physiology have emerged, including their involvement in the neuroendocrine control of ovulation and the metabolic gating of reproductive function.
321 citations
TL;DR: Accumulating data are documenting an inverse relationship between immune status, response to vaccination, health, and longevity, suggesting that the immune system becomes less effective with advancing age and that this is clinically relevant.
Abstract: Accumulating data are documenting an inverse relationship between immune status, response to vaccination, health, and longevity, suggesting that the immune system becomes less effective with advancing age and that this is clinically relevant. The mechanisms and consequences of age-associated immune alterations, designated immunosenescence, are briefly reviewed here.
302 citations
TL;DR: The use of carbon nanomaterials, mainly fullerenes and carbon nanotubes, as sorbents in the analytical process has been discussed in this article, where the authors present their use in the development of selective membranes.
Abstract: Over time, new materials have been used and incorporated in a wide variety of analytical processes. This century, technology has produced novel nanomaterials with unique properties whose use has increased in analytical sciences. Carbon nanostructures are among these new nanomaterials. This overview reports on the use of carbon nanomaterials, mainly fullerenes and carbon nanotubes, as sorbents in the analytical process. After a brief description of their main characteristics, we present their use in the development of selective membranes. Next, we describe their role as sorbent materials and stationary phases in chromatography and provide relevant examples. We also comment on the presence of carbon nanoparticles as components of electrophoretic buffers to improve both resolution and sensitivity of separations. Finally, we briefly describe other applications in which the sorption capabilities of carbon nanostructures play a role.
302 citations
TL;DR: SLIT with standardized extracts reduces both symptom scores and rescue medication use in children with allergic asthma compared with placebo, demonstrating a relevant heterogeneity due to widely differing scoring systems.
TL;DR: The election of the most adequate evolution model to take out profit from these parent selection mechanisms is tackled and it is confirmed that these three processes may enhance the operation of the parent-centric crossover operators.
TL;DR: All green manures had a positive effect on the soil biological properties, plant nutrition an crop yield parameters, although at the end of the experimental period and at the high organic matter rate, the soil microbial biomass and dehydrogenase, urease, beta-glucosidase, phosphatase and arylsulfatase activities increased more significantly in the TP amended soils.
TL;DR: The results suggest that DML2 and DML3 are required not only for removing DNA methylation marks from improperly-methylated cytosines, but also for maintenance of high methylation levels in properly targeted sites.
Abstract: Cytosine DNA methylation is a stable epigenetic mark for maintenance of gene silencing across cellular divisions, but it is a reversible modification. Genetic and biochemical studies have revealed that the Arabidopsis DNA glycosylase domain-containing proteins ROS1 (REPRESSOR OF SILENCING 1) and DME (DEMETER) initiate erasure of 5-methylcytosine through a base excision repair process. The Arabidopsis genome encodes two paralogs of ROS1 and DME, referred to as DEMETER-LIKE proteins DML2 and DML3. We have found that DML2 and DML3 are 5-methylcytosine DNA glycosylases that are expressed in a wide range of plant organs. We analyzed the distribution of methylation marks at two methylated loci in wild-type and dml mutant plants. Mutations in DML2 and/or DML3 lead to hypermethylation of cytosine residues that are unmethylated or weakly methylated in wild-type plants. In contrast, sites that are heavily methylated in wild-type plants are hypomethylated in mutants. These results suggest that DML2 and DML3 are required not only for removing DNA methylation marks from improperly-methylated cytosines, but also for maintenance of high methylation levels in properly targeted sites.
TL;DR: It is proposed that caloric restriction increases bioavailability of NO, decreases vascular reactive oxygen species generation, activates the Nrf2/antioxidant response element pathway, inducing reactive oxygen Species detoxification systems, exerts antiinflammatory effects, and, thereby, suppresses initiation/progression of vascular disease that accompany aging.
Abstract: This review focuses on the emerging evidence that attenuation of the production of reactive oxygen species and inhibition of inflammatory pathways play a central role in the antiaging cardiovascular effects of caloric restriction. Particular emphasis is placed on the potential role of the plasma membrane redox system in caloric restriction-induced pathways responsible for sensing oxidative stress and increasing cellular oxidative stress resistance. We propose that caloric restriction increases bioavailability of NO, decreases vascular reactive oxygen species generation, activates the Nrf2/antioxidant response element pathway, inducing reactive oxygen species detoxification systems, exerts antiinflammatory effects, and, thereby, suppresses initiation/progression of vascular disease that accompany aging.
TL;DR: The sometimes contradictory role attributed by scientists to lees in wine production is discussed and the present exploitation of lees is outlined.
TL;DR: Nursery-produced tomato seedlings grown in WP (65%)+MSWC (30%) displayed quality indices similar to those recorded for conventional mixtures of old and white peat sphagnum, due to a correct balance between the compost nutrient supply and the porosity and aeration provided bywhite peat.
TL;DR: It is concluded that high levels of moisture, contact time and pressure could result in higher transfer between surfaces and the identification and elimination of certain tasks or activities involving higher levels of these factors could be helpful to prevent bacterial transfer.
Abstract: Bacterial transfer events are considered to be an important cause of transmission of food-borne diseases. In this review the most common ways of bacterial transfer to food are studied, concluding that high levels of moisture, contact time and pressure could result in higher transfer between surfaces. From a risk management approach, this means that the identification and elimination of certain tasks or activities involving higher levels of these factors could be helpful to prevent bacterial transfer. Besides, mathematical bacterial transfer models from literature are analysed, highlighting the use of transfer rates distributions to model bacterial transfer in a probabilistic Quantitative Microbiological Risk Assessment (QMRA) framework.
TL;DR: Paper sheets made from pulp extracted by cooking with soda and AQ at 180 degrees C and 90 min pulp exhibit the best drainage index, breaking length, stretch and burst index.
TL;DR: In this paper, the authors measured the canopy temperature in a Central California mature pistachio orchard under full and deficit irrigation, and concluded that the CWSI, obtained from continuous nadir-view measurements with IRTs, is a good and very sensitive indicator of water stress.
Abstract: Regulated deficit irrigation (RDI) strategies, often applied in tree crops, require precise monitoring methods of water stress. Crop water stress index (CWSI), based on canopy temperature measurements, has shown to be a good indicator of water deficits in field crops but has seldom been used in trees. CWSI was measured on a continuous basis in a Central California mature pistachio orchard, under full and deficit irrigation. Two treatments—control, returning the full evapotranspiration (ETc) and RDI—irrigated with 40% ETc during stage 2 of fruit grow (shell hardening). During stage 2, the canopy temperature—measured continuously with infrared thermometers (IRT)—of the RDI treatment was consistently higher than the control during the hours of active transpiration; the difference decreasing after irrigation. The non-water-stressed baseline (NWSB), obtained from clear-sky days canopy–air temperature differential and vapour pressure deficit (VPD) in the control treatment, showed a marked diurnal variation in the intercept, mainly explained by the variation in solar radiation. In contrast, the NWSB slope remained practically constant along the day. Diurnal evolution of calculated CWSI was stable and near zero in the control, but showed a clear rising diurnal trend in the RDI treatment, increasing as water stress increased around midday. The seasonal evolution of the CWSI detected large treatment differences throughout the RDI stress period. While the CWSI in the well-irrigated treatment rarely exceeded 0.2 throughout the season, RDI reached values of 0.8–0.9 near the end of the stress period. The CWSI responded to irrigation events along the whole season, and clearly detected mild water stress, suggesting extreme sensitivity to variations in tree water status. It correlated well with midday leaf water potential (LWP), but was more sensitive than LWP at mild stress levels. We conclude that the CWSI, obtained from continuous nadir-view measurements with IRTs, is a good and very sensitive indicator of water stress in pistachio. We recommend the use of canopy temperature measurements taken from 1200 to 1500 h, together with the following equation for the NWSB: (T
c − T
a) = −1.33·VPD + 2.44. Measurements of canopy temperature with VPD < 2 kPa are likely to generate significant errors in the CWSI calculation and should be avoided.
TL;DR: A simple approach to obtain reliable estimates of the effective population size in real world populations via the computation of the increase in inbreeding for each individual (delta Fi) in a given population using a pre-defined reference subset.
Abstract: We present here a simple approach to obtain reliable estimates of the effective population size in real world populations via the computation of the increase in inbreeding for each individual (delta Fi) in a given population. The values of delta Fi are computed as t-root of 1 � (1 � Fi) where Fi is the inbreeding coefficient and t is the equivalent complete generations for each individual. The values of delta F computed for a pre-defined reference subset can be averaged and used to estimate effective size. A standard error of this estimate of Ne can be further computed from the standard deviation of the individual increase in inbreeding. The methodology is demonstrated by applying it to several simulated examples and to a real pedigree in which other methodologies fail when considering reference subpopulations. The main characteristics of the approach and its possible use are discussed both for predictive purposes and for analyzing genealogies. effective size / increase in inbreeding / overlapped generation / genetic contribution
TL;DR: The application of beet vinasse deteriorates the soil and therefore does not contribute to its restoration, but the application of TP, and BV composted with TP protects the soils and will contribute toIts restoration.
TL;DR: When used in combination with paricalcitol, AMG 641 provided excellent control of secondary hyperparathyroidism and prevented mortality associated with the use of vitamin D derivatives without causing tissue calcification.
TL;DR: A new removable interface that enables the introduction of the extracted analytes into the GC system, while preventing the ionic liquid from entering the column, has been developed.
Abstract: The use of ionic liquids as extracting media in single-drop liquid-phase microextraction (SDME) and its direct coupling to gas chromatography/mass spectrometry (GC/MS) is presented. For this purpose, a new removable interface that enables the introduction of the extracted analytes into the GC system, while preventing the ionic liquid from entering the column, has been developed. The determination of three representative pollutants in water samples has been used as a model analytical problem in order to demonstrate the feasibility of the proposed interface. The analytes (dichloromethane, p-xylene, and n-undecane) were coextracted from the aqueous sample in a 2-microL drop of 1-butyl-3-methylimidazolium hexaflourophosphate. Then, the syringe used to perform the SDME was directly introduced into the interface, which was held at 140 degrees C in order to achieve a complete volatilization of the target compounds. After the injection, the ionic liquid was retained in the interface, while a carrier gas transferred the volatilized analytes into the GC inlet. The optimization of the operational variables affecting the new interface (temperature, carrier flow rate, sample volume and injection technique) was accomplished. The analytes could be determined with detection limits in the low-nanogram per milliliter concentration range, and the relative standard deviations were between 3.3 and 4.4%.
TL;DR: Results for olive trees suggest genetic variability in olive cultivars in relation to potassium requirements for stem growth and the regulation of water transpiration, and inhibition of the stomatal closure mechanism produced by moderate potassium starvation is a widespread plant physiological disorder.
TL;DR: The developed method allows the determination of benzene, toluene, ethylbenzene and xylenes isomers in water under the reference concentration level fixed by the international legislation.
TL;DR: The results demonstrate the SSF-based strategy is a successful approach for the production of a generic feedstock from wheat, and that this feedstock can be efficiently utilised for succinic acid production.
TL;DR: The energy cost required for ammonium assimilation is lower than that of nitrate, and many species use ammonium preferentially, but nitrate is the nitrogen source most preferred because of its major abundance.
Abstract: Ammonium and nitrate are primary nitrogen sources for many organisms. Though the energy cost required for ammonium assimilation is lower than that of nitrate ([2][1]) and many species use ammonium preferentially, nitrate is the nitrogen source most preferred because of its major abundance (about 10
TL;DR: The results suggest that white lupin's release of flavonoids into the rhizosphere plays a significant role in its efficient P-acquisition strategy by solubilizing Fe-bound P and by limiting the microbial mineralization of citrate.
Abstract: The impact of flavonoids released by phosphorus-deficient white lupin roots on inorganic P and soil microorganisms is largely unknown. We report that flavonoids isolated from white lupin roots mobilized inorganic phosphorus and decreased soil microbial respiration, citrate mineralization, and soil phosphohydrolase activities, but did not reduce the soil ATP content. The results suggest that white lupin's release of flavonoids into the rhizosphere plays a significant role in its efficient P-acquisition strategy by solubilizing Fe-bound P and by limiting the microbial mineralization of citrate.
TL;DR: In this article, the authors provide an overview of the archaeological, chronological and palaeoenvironmental data from the end of the Middle Palaeolithic period to the Epipalaeolithic.