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High Predictive Power (high + predictive_power)
Selected AbstractsPredictive 3D-Quantitative Structure-Activity Relationship for A1 and A2A Adenosine Receptor LigandsMOLECULAR INFORMATICS, Issue 11-12 2009Olga Yuzlenko Abstract The use of QSAR applications to develop adenosine receptor (AR) antagonists is not so common. A library of all xanthine derivatives, obtained at the Department of Technology and Biotechnology of Drugs, was created. Sixty-three active adenosine A1 receptor ligands and one hundred thirty nine active adenosine A2A receptor ligands were used for 3D-QSAR investigation. The 3D-QSAR equations with a high predictive power in estimating the binding affinity values of potential A1 and A2A ARs ligands were derived. For the first time, hybrid shape-property descriptors were used in 3D-QSAR for xanthine ARs ligands. The obtained models were characterized by a high regression and cross-validation coefficients. Two types of the model validation were tested , dividing the library into the training set for model development and external set for model validation and increasing the number of library components and checking the model by cross-validated regression coefficient. The analysis of the results depicts that for the A1 AR binding activity it is important for ligands to possess R1 -propyl substituents along with the phenyl or benzyl substituents bearing halogen atom and phenethyl moiety. For A2A AR affinity it could be favorable to introduce phenethyl or phenyl substituent connected with the tricyclic ring by the alkoxy chain. The nature of R1 group may not significantly affect the A2A AR affinity. High predictive power of the equations suggests their use for further development of adenosine receptor antagonists within xanthine derivatives. [source] HIGH-DIMENSIONAL LEARNING FRAMEWORK FOR ADAPTIVE DOCUMENT FILTERING,COMPUTATIONAL INTELLIGENCE, Issue 1 2003Wai Lam We investigate the unique requirements of the adaptive textual document filtering problem and propose a new high-dimensional on-line learning framework, known as the REPGER (relevant feature pool with good training example retrieval rule) algorithm to tackle this problem. Our algorithm possesses three characteristics. First, it maintains a pool of selective features with potentially high predictive power to predict document relevance. Second, besides retrieving documents according to their predicted relevance, it also retrieves incoming documents that are considered good training examples. Third, it can dynamically adjust the dissemination threshold throughout the filtering process so as to maintain a good filtering performance in a fully interactive environment. We have conducted experiments on three document corpora, namely, Associated Press, Foreign Broadcast Information Service, and Wall Street Journal to compare the performance of our REPGER algorithm with two existing on-line learning algorithms. The results demonstrate that our REPGER algorithm gives better performance most of the time. Comparison with the TREC (Text Retrieval Conference) adaptive text filtering track participants was also made. The result shows that our REPGER algorithm is comparable to them. [source] Neophyte species richness at the landscape scale under urban sprawl and climate warmingDIVERSITY AND DISTRIBUTIONS, Issue 6 2009Michael P. Nobis Abstract Aim, Land use and climate are two major components of global environmental change but our understanding of their simultaneous and interactive effects upon biodiversity is still limited. Here, we investigated the relationship between the species richness of neophytes, i.e. non-native vascular plants introduced after 1500 AD, and environmental covariates to draw implications for future dynamics under land-use and climate change. Location, Switzerland, Central Europe. Methods, The distribution of vascular plants was derived from a systematic national grid of 1 km2 quadrates (n = 456; Swiss Biodiversity Monitoring programme) including 1761 species, 122 of which were neophytes. Generalized linear models (GLMs) were used to correlate neophyte species richness with environmental covariates. The impact of land-use and climate change was thereafter evaluated by projections for the years 2020 and 2050 using scenarios of moderate and strong changes for climate warming (IPCC) and urban sprawl (NRP 54). Results, Mean annual temperature and the amount of urban areas explained neophyte species richness best, with a high predictive power of the corresponding model (cross-validated D2 = 0.816). Climate warming had a stronger impact on the potential increase in the mean neophyte species richness (up to 191% increase by 2050) than ongoing urban sprawl (up to 10% increase) independently from variable interactions and model extrapolations to non-analogue environments. Main conclusions, In contrast to other vascular plants, the prediction of neophyte species richness at the landscape scale in Switzerland requires few variables only, and regions of highest species richness of the two groups do not coincide. The neophyte species richness is basically driven by climatic (temperature) conditions, and urban areas additionally modulate small-scale differences upon this coarse-scale pattern. According to the projections climate warming will contribute to the future increase in neophyte species richness much more than ongoing urbanization, but the gain in new neophyte species will be highest in urban regions. [source] Responses of riparian plants to flooding in free-flowing and regulated boreal rivers: an experimental studyJOURNAL OF APPLIED ECOLOGY, Issue 6 2002M. E. Johansson Summary 1The long history of river regulation has resulted in extensively changed ecosystem structures and processes in rivers and their associated environments. This fact, together with changing climatic and hydrological conditions, has increased the need to recover the natural functions of rivers. To develop guidelines for river restoration, comparative ecological experiments at contrasting water-level regimes are needed. We compared growth and survival of transplanted individuals of four riparian plant species (Betula pubescens, Carex acuta, Filipendula ulmaria and Leontodon autumnalis) over 2 years on four free-flowing and four regulated riverbank sites in northern Sweden. The species were chosen as representatives of dominating life-forms and species traits on different elevations of the riverbanks. 2In Betula and Filipendula, mean proportional growth rates were significantly higher at free-flowing sites than at regulated sites, whereas no consistent differences between free-flowing and regulated sites were found in Carex and Leontodon. Differences among species were generally in accordance with natural distribution patterns along riverbank elevation gradients and with experimental evidence on flooding tolerance, although plants of all species survived and even showed positive growth rates on elevations below their natural range of occurrence. 3Partial least squares regression was used to relate plant performance (growth and survival) to duration, frequency and timing of flooding at the different sites. Flood duration and frequency typically reduced performance in all species and during all time periods, although to various degrees. Flood events early in the experiment determined the outcome to a high degree at all sites. Variables indicating a regulated regime were mostly negatively related to plant performance, whereas free-flowing regime variables were positively related to plant performance. 4We used two of the regression models generated from our data with an acceptably high predictive power to simulate a hypothetical re-regulation scenario in run-of-river impoundments. With an overall reduction in flooding duration and frequency of 50,75%, plant performance of Filipendula at low riverbank elevations showed predicted increases of about 20,30%, levelling off to zero at the highest elevations. Reductions in summer floods represented about one-third to half of this increase. 5We conclude that for a range of species individual plant performance is clearly reduced on banks of impoundments and storage reservoirs due to changes in the water-level regime. Furthermore, our model simulation suggests that rather substantial reductions of flood duration and frequency are needed to improve plant performance on riverbanks upstream from dams in impounded rivers. River restoration principles should, however, be based on a combination of experimental data on plant performance of individual species and observed long-term changes in plant communities of regulated rivers. Consequently, successful re-regulation schemes in boreal rivers should include both reductions of summer and winter floods as well as re-introduced spring floods. [source] Clinical indicators of ineffective airway clearance in children with congenital heart diseaseJOURNAL OF CLINICAL NURSING, Issue 5 2009Viviane Martins Da Silva Aims and objectives., To analyse the sensitivity and specificity of clinical indicators of ineffective airway clearance in children with congenital heart disease and to identify the indicators that have high predictive power. Background., The precise establishment of nursing diagnoses has been found to be one of the factors contributing to higher quality of care and cost reduction in healthcare institutions. The use of indicators to diagnose ineffective airway clearance could improve care of children with congenital heart disease. Design., Longitudinal study. Methods., Participants consisted of 45 children, ,1 year of age, with congenital heart disease, who had not had definitive or palliative surgical correction. Six assessments were made at 2-day intervals. Each clinical indicator was defined based on previously established operational criteria. Sensitivity, specificity and positive and negative predictive values of each indicator were calculated based on a model for the longitudinal data. Results., A nursing diagnosis of ineffective airway clearance was made in 31% of patients on the first assessment, rising to 71% on the last assessment, for a 40% increase. Sensitivity was highest for Changes in Respiratory Rates/Rhythms (0·99), followed by Adventitious Breath Sounds (0·97), Sputum Production (0·85) and Restlessness (0·53). Specificity was higher for Sputum Production (0·92), followed by Restlessness (0·73), Adventitious Breath Sounds (0·70) and Changes in Respiratory Rates/Rhythms (0·17). The best positive predictive values occurred for Sputum Production (0·93) and Adventitious Breath Sounds (0·80). Conclusions., Adventitious Breath Sounds followed by Sputum Production were the indicators that had the best overall sensitivity and specificity as well as the highest positive predictive values. Relevance to clinical practice., The use of simple indicators in nursing diagnoses can improve identification of ineffective airway clearance in children with congenital heart disease, thus leading to early treatment of the problem and better care for these children. [source] THE USE OF NEAR INFRARED REFLECTANCE SPECTROMETRY FOR CHARACTERIZATION OF BROWN ALGAL TISSUE,JOURNAL OF PHYCOLOGY, Issue 5 2010Kyra B. Hay Measuring qualitative traits of plant tissue is important to understand how plants respond to environmental change and biotic interactions. Near infrared reflectance spectrometry (NIRS) is a cost-, time-, and sample-effective method of measuring chemical components in organic samples commonly used in the agricultural and pharmaceutical industries. To assess the applicability of NIRS to measure the ecologically important tissue traits of carbon, nitrogen, and phlorotannins (secondary metabolites) in brown algae, we developed NIRS calibration models for these constituents in dried Sargassum flavicans (F. K. Mertens) C. Agardh tissue. We then tested if the developed NIRS models could detect changes in the tissue composition of S. flavicans induced by experimental manipulation of temperature and nutrient availability. To develop the NIRS models, we used partial least squares regression to determine the statistical relationship between trait values determined in laboratory assays and the NIRS spectral data of S. flavicans calibration samples. Models with high predictive power were developed for all three constituents that successfully detected changes in carbon, nitrogen, and phlorotannin content in the experimentally manipulated S. flavicans tissue. Phlorotannin content in S. flavicans was inversely related to nitrogen availability, and nitrogen, temperature, and tissue age interacted to significantly affect phlorotannin content, demonstrating the importance of studies that investigate these three variables simultaneously. Given the speed of analysis, accuracy, small tissue requirements, and ability to measure multiple traits simultaneously without consuming the sample tissue, NIRS is a valuable alternative to traditional methods for determining algal tissue traits, especially in studies where tissue is limited. [source] Predictive 3D-Quantitative Structure-Activity Relationship for A1 and A2A Adenosine Receptor LigandsMOLECULAR INFORMATICS, Issue 11-12 2009Olga Yuzlenko Abstract The use of QSAR applications to develop adenosine receptor (AR) antagonists is not so common. A library of all xanthine derivatives, obtained at the Department of Technology and Biotechnology of Drugs, was created. Sixty-three active adenosine A1 receptor ligands and one hundred thirty nine active adenosine A2A receptor ligands were used for 3D-QSAR investigation. The 3D-QSAR equations with a high predictive power in estimating the binding affinity values of potential A1 and A2A ARs ligands were derived. For the first time, hybrid shape-property descriptors were used in 3D-QSAR for xanthine ARs ligands. The obtained models were characterized by a high regression and cross-validation coefficients. Two types of the model validation were tested , dividing the library into the training set for model development and external set for model validation and increasing the number of library components and checking the model by cross-validated regression coefficient. The analysis of the results depicts that for the A1 AR binding activity it is important for ligands to possess R1 -propyl substituents along with the phenyl or benzyl substituents bearing halogen atom and phenethyl moiety. For A2A AR affinity it could be favorable to introduce phenethyl or phenyl substituent connected with the tricyclic ring by the alkoxy chain. The nature of R1 group may not significantly affect the A2A AR affinity. High predictive power of the equations suggests their use for further development of adenosine receptor antagonists within xanthine derivatives. [source] Quantitative Structure,Activity Relationship Models for Predicting Biological Properties, Developed by Combining Structure- and Ligand-Based Approaches: An Application to the Human Ether-a-go-go-Related Gene Potassium Channel InhibitionCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2009Alessio Coi A strategy for developing accurate quantitative structure,activity relationship models enabling predictions of biological properties, when suitable knowledge concerning both ligands and biological target is available, was tested on a data set where molecules are characterized by high structural diversity. Such a strategy was applied to human ether-a-go-go-related gene K+ channel inhibition and consists of a combination of ligand- and structure-based approaches, which can be carried out whenever the three-dimensional structure of the target macromolecule is known or may be modeled with good accuracy. Molecular conformations of ligands were obtained by means of molecular docking, performed in a previously built theoretical model of the channel pore, so that descriptors depending upon the three-dimensional molecular structure were properly computed. A modification of the directed sphere-exclusion algorithm was developed and exploited to properly splitting the whole dataset into Training/Test set pairs. Molecular descriptors, computed by means of the codessa program, were used for the search of reliable quantitative structure,activity relationship models that were subsequently identified through a rigorous validation analysis. Finally, pIC50 values of a prediction set, external to the initial dataset, were predicted and the results confirmed the high predictive power of the model within a quite wide chemical space. [source] Gastropods on Submersed Macrophytes in Yangtze Lakes: Community Characteristics and Empirical ModellingINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2006Hai-Jun Wang Abstract Epiphytic gastropods in Yangtze lakes have suffered from large-scale declines of submersed macrophytes during past decades. To better understand what controls gastropod community, monthly investigations were carried out in four Yangtze lakes during December, 2001,March, 2003. Composed of 23 species belonging to Pulmonata and Prosobranchia, the community is characterized by the constitution of small individuals. The average density and biomass were 417 ± 160 ind/m2 and 18.05 ± 7.43 g/m2, with maxima around August. Submersed macrophyte biomass is shown to be the key factor affecting species number, density, and biomass of gastropods. Accordingly, a series of annual and seasonal models yielding high predictive powers were generated. Preference analyses demonstrated that pulmonates and prosobranchs with different respiratory organs prefer different macrophyte functional groups. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||