Home About us Contact
|
Home About us Contact | ||
|
|
||
Precise Prediction (precise + prediction)
Selected AbstractsA new index of habitat alteration and a comparison of approaches to predict stream habitat conditionsFRESHWATER BIOLOGY, Issue 10 2007BRIAN FRAPPIER Summary 1. Stream habitat quality assessment complements biological assessment by providing a mechanism for ruling out habitat degradation as a potential stressor and provides reference targets for the physical aspects of stream restoration projects. This study analysed five approaches for predicting habitat conditions based on discriminant function, linear regressions, ordination and nearest neighbour analyses. 2. Quantitative physical and chemical habitat and riparian conditions in minimally-impacted streams in New Hampshire were estimated using United States Environmental Protection Agency's Environmental Monitoring and Assessment Program protocols. Catchment-scale descriptors were used to predict segment-scale stream channel and riparian habitat, and the accuracy and precision of the different modelling approaches were compared. 3. A new assessment index comparing and summarizing the degree of correspondence between predicted and observed habitat based on Euclidean distance between the standardized habitat factors is described. Higher index scores (i.e. greater Euclidean distance) would suggest a greater deviation in habitat between observed conditions and expected reference conditions. As in most biotic indices, the range in index scores in reference sites would constitute a situation equivalent to reference conditions. This new index avoids the erroneous prediction of multiple, mutually exclusive habitat conditions that have confounded previous habitat assessment approaches. 4. Separate linear regression models for each habitat descriptor yielded the most accurate and precise prediction of reference conditions, with a coefficient of variation (CV) between predictions and observations for all reference sites of 0.269. However, for a unified implementation in regions where a classification-based approach has already been taken for biological assessment, a discriminant analysis approach, that predicted membership in biotic communities and compared the mean habitat features in the biotic communities with the observed habitat features, was similar in prediction accuracy and precision (CV = 0.293). 5. The best model had an error of 27% of the mean index value for the reference sites, indicating substantial room for improvement. Additional catchment characteristics not readily available for this analysis, such as average rainfall or winter snow-pack, surficial geological characteristics or past land-use history, may improve the precision of the predicted habitat features in the reference streams. Land-use history in New Hampshire and regional environmental impacts have greatly impacted stream habitat conditions even in streams considered minimally-impacted today; thus as regional environmental impacts change and riparian forests mature, reference habitat conditions should be re-evaluated. [source] Proteomic identification of biomarkers related to Helicobacter pylori -associated gastroduodenal disease: Challenges and opportunitiesJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 11 2008Ming-Shiang Wu Abstract Helicobacter pylori colonize the stomach of over half the world's population. While 80,90% H. pylori -infected individuals have clinically asymptomatic gastritis, 10,15% develop peptic ulcer, and 1,2% gastric malignancies. These variable clinical outcomes have led to an interest in prognostic indicators. The current disease paradigm suggests that host genetics and bacterial virulence both play important roles in modulating the final outcome of H. pylori infection. Elucidation of the interaction between host and bacterium is essential to clarify pathogenesis and to develop new strategies for prevention and treatment. Proteomic technology is a powerful tool for simultaneously monitoring proteins and protein variation on a large scale in biological samples. It has provided an unprecedented opportunity to survey a cell's translational landscape comprehensively, and the results may allow in-depth analyses of host and pathogen interactions. Using this high-throughput platform and taking advantage of complete sequences for both the H. pylori and the human genome in available databases, we have identified several crucial proteins that have pathogenic and prognostic potential. Among them, antibodies to AhpC and GroEs of H. pylori could be utilized for identification of patients who are at high risk of disease complications after H. pylori infection. Evolving proteomic technologies, together with appropriate clinical phenotyping and genotype information should enhance understanding of disease pathogenesis and lead to more precise prediction of variable disease outcomes. It will also facilitate development of biomarkers for diagnosis, treatment, and prevention of H. pylori infection. [source] Prediction of response to treatment of chronic hepatitis B with pegylated interferon in the PhilippinesJOURNAL OF MEDICAL VIROLOGY, Issue 2 2010Dorothy M. Agdamag Abstract The response marker for interferon has not been investigated fully for hepatitis B viruses (HBVs) in the Philippines where novel subtypes B5 and C5 were recognized recently. The prediction parameters for interferon treatment were assessed, with emphasis on the mutation patterns in the basal core promoter and precore regions in patients with chronic hepatitis B. Seventeen HBeAg-positive patients were stratified according to response to treatment with pegylated interferon based on HBe seroconversion and HBV load. Intra-patient distributions of wild-type strains (A1762, G1764) and variants (T1762, A1764) were analyzed using HBV-DNA amplification and subsequent molecular cloning. The rate of variants (T1762, A1764) harbored by a patient was higher among responders (41.2% and 31% per person on average) than among non-responders (2.4% and 2.4%) to treatment with pegylated interferon at the baseline, respectively (P,<,0.05). The rate of variants (T1762, A1764) harbored by responders (41.2% and 31%) decreased to 1.7% and 1.7%, and wild-type strains (A1762, G1764) conversely became majority (98.3% and 98.3%) after treatment with pegylated interferon, respectively. HBV strains harbored by two of six responders and a patient with lower baseline load (1.0,×,104,copies/ml) showed genotype shift from A to other genotypes, where genotype A disappeared preferentially after the loss of HBeAg and genotypes B and C formed a major population. These results suggest that the HBV variants (T1762, A1764) and HBV genotype A in the Philippines have an advantage in the response to pegylated interferon. These results warrant a large-scale examination for further precise prediction of the response to treatment with interferon. J. Med. Virol. 82:213,219, 2010. © 2009 Wiley-Liss, Inc. [source] Conservation ecology of Primula sieboldii: Synthesis of information toward the prediction of the genetic/demographic fate of a populationPLANT SPECIES BIOLOGY, Issue 1 2005IZUMI WASHITANI Abstract In an age of deepening biodiversity crisis, plant species biological studies integrating ecological and genetic approaches, especially exhaustive studies with a model plant species, are urgently needed for both assessing the present status and implementing effective conservation measures, as a comprehensive understanding of demographic/genetic interactions involved in the vicious cycle of plant population extinction is a prerequisite for any precise prediction regarding plant conservation. In this article, we summarize the major contributions to conservation ecological studies on a heterostylous clonal herb Primula sieboldii, focusing on gene flow and reproductive success, which are dependent on the life-history traits of the species and biological interactions with its effective pollinators, long-tongued bumblebees. [source] Quantifying Process Tradeoffs in the Operation of Chromatographic SequencesBIOTECHNOLOGY PROGRESS, Issue 4 2003Sheau-Huey Ngiam A method for the rapid representation of key process tradeoffs that need to be made during the analysis of chromatographic sequences has been proposed. It involves the construction of fractionation and maximum purification factor versus yield diagrams, which can be completed easily on the basis of chromatographic data. The output of the framework developed reflects the degree of tradeoff between levels of yield and purity and provides a fast and precise prediction of the sample fraction collection strategy needed to meet a desired process specification. The usefulness of this approach for the purposes of product purification and contaminant removal in a single chromatographic step has been successfully demonstrated in an earlier paper and it is now extended by application to a chromatographic sequence: the separation of a hypothetical three-component protein system by hydrophobic interaction chromatography (HIC) followed by size exclusion chromatography (SEC). The HIC operation has a strong impact upon the subsequent SEC step. The studies show how the analysis of performance in such a chromatographic sequence can be carried out easily and in a straightforward fashion using the fractionation diagram approach. The methodology proposed serves as a useful tool for identifying the process tradeoffs that must be made during operation of a sequence of chromatographic steps and indicates the impact on further processing of the cut-point decisions that are made. [source] Computational significance of transient dynamics in cortical networksEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2008Daniel Durstewitz Abstract Neural responses are most often characterized in terms of the sets of environmental or internal conditions or stimuli with which their firing rate are correlated increases or decreases. Their transient (nonstationary) temporal profiles of activity have received comparatively less attention. Similarly, the computational framework of attractor neural networks puts most emphasis on the representational or computational properties of the stable states of a neural system. Here we review a couple of neurophysiological observations and computational ideas that shift the focus to the transient dynamics of neural systems. We argue that there are many situations in which the transient neural behaviour, while hopping between different attractor states or moving along ,attractor ruins', carries most of the computational and/or behavioural significance, rather than the attractor states eventually reached. Such transients may be related to the computation of temporally precise predictions or the probabilistic transitions among choice options, accounting for Weber's law in decision-making tasks. Finally, we conclude with a more general perspective on the role of transient dynamics in the brain, promoting the view that brain activity is characterized by a high-dimensional chaotic ground state from which transient spatiotemporal patterns (metastable states) briefly emerge. Neural computation has to exploit the itinerant dynamics between these states. [source] Predicting the effects of perturbations on ecological communities: what can qualitative models offer?JOURNAL OF ANIMAL ECOLOGY, Issue 5 2005DAVE RAMSEY Summary 1Quantitative predictions of the effects of perturbations on communities of interacting species have often proved to be difficult. However, if precise predictions are not a requirement then qualitative models of community dynamics offer an alternative method for predicting species responses to perturbations. 2We used two qualitative modelling approaches to predict the effects of predator control on the fledging rate of an endangered New Zealand bird, the North Island kokako. The first approach was based on loop analysis and provided predictions on the probable direction of change in species abundances to single species perturbations. The second approach, ,fuzzy interaction webs', used fuzzy logic in the framework of a fuzzy cognitive map to provide predictions on the probable magnitude of change in species abundances to perturbations. 3Using both methods, we predicted the qualitative change in the equilibrium fledging rates of kokako under various regimes of single- and multispecies predator control (ship rats, brushtail possums and stoats). Single species control was insufficient to lift the fledging rate from ,low' to ,moderate'. However, simultaneous control of both ship rats and possums had the greatest influence on the fledging rates compared with any other combination as a result of the additional indirect effect of ship rat control on stoat abundance. 4We propose qualitative modelling of community dynamics as a method suitable for predicting the effects of perturbations in complex ecological communities that can encapsulate diverse sources of knowledge about food web interactions. We believe that these methods are a useful set of heuristic tools that can be used to propose testable hypotheses about ecosystem functioning that can complement existing statistical and quantitative modelling approaches. [source] | ||||||||||