Application of the recommendation architecture for discovering associative similarities in text

We investigate the use of the Recommendation Architecture (RA) for discovering associative similarities in text documents. RA is a connectionist model that simulates the pattern synthesizing and pattern recognition functions of the human brain. For this purpose a set of experiments has been carried out to adjust the parameters of the system to classify newsgroup postings belonging to 10 different categories. The variation and the poor quality of such a data set poses an interesting challenge to any intelligent classification system. A suitable feature selection scheme is devised to represent the input document set. Then the input is organized by the system into a hierarchy of repeating patterns that sets up a preferred path to the output. We report on the key findings of this experiment and the features of the Recommendation Architecture model that makes it suitable for classification of noisy and complex real world data

Rainfall forecasting for flood prediction in the Nilwala basin

Flooding is the major natural disaster in Sri Lanka and reliable forecasts with longer lead time is a way of reducing the damages. In this study a weather model was coupled with a hydrologic model and a hydraulic model for predicting floods in Nilwala river basin in southern Sri Lanka. WRF 3.0 (Weather Research and Forecasting) weather model was configured and used to predict rainfall over the basin 24 h into future. The model was configured by investigating the impacts of its physics options on precipitation forecasting. The impacts of microphysics schemes, cumulus schemes, land surface schemes, long/shortwave schemes and boundary layer schemes on rainfall predictions were investigated. The predictions were compared with observed point rainfall data for three rainfall events to find reasonably good physics combination. It was seen that model physics combination; Ferrier microphysics scheme, Kain-Fritsch cumulus scheme, Rapid Update Curve land surface scheme, Rapid Radiative Transfer Model longwave radiation scheme, Dudhia shortwave scheme and Yonsei boundary layer scheme yields better precipitation predictions over the basin. Output of the weather model was coupled with hydrologic model HEC-HMS 3.3 (Hydrologic Engineering Center-Hydrologic Modeling System) with Clark’s, Snyder’s and SCS transformation methods. In all model runs Green-Ampt loss model was executed with recession base flow method. Before using the model with the WRF output HEC-HMS model was calibrated for historical events and Snyder’s method performed better than other methods in calibration and verification. Snyder’s method produced Nash-Sutcliff efficiencies greater than 70% and 50% in calibration and verification respectively. WRF predicted rainfall for May-2003 was introduced to HEC-HMS and the generated river discharges of sub basin were ingested to the HEC-RAS 4.0 (Hydrologic Engineering Center-River Analysis System) hydraulic model for water profile computations along the Nilwala main river. Output of HEC-RAS was exported to Arc- GIS 9.2 where it was two dimensionally visualized as a flood map. Model was capable of predicting the areas as inundated regions but with underestimation of inundation depth

Statistical model to predict contour elevation using shuttle radar topographic mission digital elevation data

This study is based on two geographical datasets, namely, Shuttle Radar Topographic Mission (SRTM) elevation and contour elevation. The SRTM data is available for all locations in Sri Lanka. It follows the shape of the actual ground but not the actual elevation of the surface. This is due to errors introduced during processing. The contour data is obtained from the actual ground survey data of contour maps and using ArcGIS software. The survey data is more reliable, but more expensive. Since it does not contain ground level variations, Sri Lanka does not have contour elevations at all locations. Measuring contour elevation for all locations is a costly procedure. Therefore, finding a method to evaluate the approximated value of contour elevation with a less costly method is essential. Thus the objective of this study is to find a statistical model to predict the contour elevation based on SRTM data. Both types of data are available only for four locations: Paddhiruppu, Kegalle, Badulla, and Katharagama, in Sri Lanka. According to the geography of Sri Lanka, three clusters are distinguishable by elevation. These are the Central Highlands, the Plains, and the Coastal belt. Since the data used in this study are for four different locations and these locations fall into three different clusters, three regression models are fitted for each cluster and the models are validated. Multiple, linear regression analysis is used to fit the models. The t- test is used to test the significance of parameters while the F- test is used to test the significance of the overall model. Residual analysis is carried out to test the normality, homoscedasticity and auto correlation of the residuals. The goodness of the fitted model is evaluated by the coefficient of determination 2 R . Approximately 99% of the variation is explained by the fitted models and 82% by the validated model. Thus, if the SRTM data value is known, by choosing the appropriate model based on its cluster, the approximated contour elevation could be predicted

COMPOSITION, STRUCTURE AND ORGANIZATION OF MIXED-SPECIES BIRD FLOCKS IN WALAUWA TTA-WA TURANA SWAMP FOREST, KALUTARA DISTRICT, WESTERN PROVINCE OF SRI LANKA

Mixed- species foraging bird flocks in Walauwatta-Waturan Swamp Forest (WWSF) were studiedfor a period of six months from February to July in 2001. Field data was collected from 07:00 to18:00 hrs and flocks were followed as long as possible to record their composition. Scan samplingmethod (Altman, 1975) was used to record their behavioural activity, height of feeding, feedingsite and the role of each individual within the flock. Two minute scan samples were done with fiveminute intervals and almost all the birds participating in the flock were scanned within the twominutes time period.The flocking tendency of birds in WWSF was 28.7% and 27 flocks were studied. A total of 31 birdspecies were recorded to participate in mixed-species flocks in WWSF. These include 28 residentand 3 migrate species. Five species were endemic to Sri Lanka. The flock composition varied from3 to 15 species (5.89±2.61) and 4 to 31 individuals (I2.96±7.41). There was a positive correlationbetween the number of species and ~ock size (r= 0.796).Crested Drongo (77.78%) and Black-naped Monarch (70.37%) were the most frequent birds foundin flocks while Sri Lanka Orange-billed Babbler was the most abundant (8.78±3.67 individuals perflock). Territorial species such as Purple-romped Sunbird joined the flock when it was passingthrough their territory. Birds in mixed-species flocks in WWSF were classified as nuclear species,lead species, regular species, and occasional species. 2 major nuclear species (Crested Drongo &Sri Lanka Orange-billed Babbler), 4 lead species (Above two with Malabar Trogon and AsianParadise Flycatcher), 12 regular species, and IS occasional species were identified. Associations ofbird species participating in mixed species flocks in WWSF were studied using cluster analysis.Two main clusters could be identified, one of which could be again divided into two subassociations.The first cluster comprised of Crested Drongo and Black-naped Monarch who showedthe highest level of association. Black Bulbul and Sri Lanka Orange-billed Babbler could not bepooled into any clusters.Different species in mixed species flocks had different optimum height levels of movementthrough the forest and appeared to have characteristic feeding sites. The vertical distribution of theregular species in flocks was consistent. Sri Lanka Orange-billed Babbler was found at a widerange of foraging heights. But, Scarlet Minivet and Black Bulbul were observed mostly in thecanopy and the Crested Drongo was observed in the middle strata of the forest (10 to 20 ft). TheAsian Paradise Flycatcher was observed in the same range. However, other fly catching species(Black-naped Monarch and Tickell's Blue flycatcher) were observed mostly in the 10 to 15ftvertical range. There was an extensive overlap of height ranges between some species. But theywere observed to use different activity/feeding sites. Black-naped Monarch and Velvet-frontedBlue Nuthatch were found in the same height range, but feeding sites utilized by them wasdifferent (foliage and tree trunk respectively). Crested Drongo and Asian Paradise Flycatcher wereobserved to occupy the same vertical height range and feeding sites, but they were using differentfeeding techniques. Even being a small area of 12 ha (CEA, 1994) IIWTOUIIdedby Rubber plantations and homegardens, the Swamp Forest have a considerable flocking tendency with compared to Sinharaja Forest Reserve 30%)(Kotagama et. AI., 1986) and Knuckles Conservation Forest (30.S) (Sbriyani, 2000), thus worth conserve thehabitat

COMPARISON OF FLORISTIC DIVERSITY OF FOUR WOODLAND TYPES IN THE UPPER HANTANA CAMPUS LAND

In the Upper Hantana campus land, three broad-leaf woodlands Peresereanthes fa/cataria.A /stonia macrophylla, or mixed species woodland and Pinus caribaea woodland grow inproximity to one another. The wide range of floristic diversity exhibited by these differentwoodlands was compared using plot sampling.The overstorey vegetation of the Alstonia woodland showed the highest, i) density, ii)floristic richness, iii) proportion of endemics and iv) plant diversity, foIlowed in decreasingorder by that in the Peresereanthes-, mixed-, and Pinus woodland. In the understoreyvegetation, floristic diversity «10 ern) was highest in Peresereanthes woodland, foIlowedin decreasing order by that in Alstonia-, mixed species-, and Pinus woodlands. Speciesrank abundance plots of overstorey and understorey species show that over storeyvegetation in Pinus woodland, fits the geometric series, whereas the others fit the logseries or log normal model.The broad-leaf species woodlands in Upper Hantana also showed better naturalregeneration of an array of species. AIl woodlands showed differences in micro-siteconditions. Levels of human disturbance and burning may contribute to differencesamongst them. These results provide baseline ecological information on naturalregeneration in different woodland types and indicate their relative potential forconservation of biodiversity and water resources.

Differential effects on inhibition of cholesterol absorption by plant stanol and plant sterol esters in apoE−/− mice

Aims 'Functional foods'; supplemented with plant sterol esters (PSE) and plant stanol esters (PSA) are therapeutic options for the management of hypercholesterolaemia. However, their effects on blood monocytes, endothelial function, atherogenesis, and sterol tissue concentrations are poorly understood. Methods and results Male apoE−/− mice (n= 30) were randomized to three different diets for 6 weeks (n= 10 per group): high-cholesterol (1.25%) western-type diet (WTD), WTD + 2% PSE, and WTD + 2% PSA. Both supplements reduced serum cholesterol. WTD + PSE resulted in increased plant sterol serum concentrations and increased inflammatory Ly-6C(high) monocyte numbers. WTD + PSA increased plant stanol serum concentrations and Ly-6C-monocyte numbers, but decreased vascular superoxide release, lipid hydroperoxides, and inflammatory cytokines in aortic tissue, in plasma, and in circulating monocytes. Despite reduced serum cholesterol concentrations, both supplements impaired endothelial vasodilation compared with WTD. WTD + PSA reduced the development of atherosclerotic lesions compared with WTD alone (12.7 ± 3.7 vs. 28.3 ± 3.5%), and WTD + PSE was less effective (17.5 ± 3.7%). WTD + PSE and WTD + PSA reduced the cholesterol content in the liver, but not in the brain. However, WTD + PSE and WTD + PSA increased plant sterol and plant stanol concentrations in the liver as well as in the brain. Conclusion PSE and PSA supplementation reduced serum cholesterol, but increased plant sterol and plant stanol concentrations. Elevated levels of PSE and PSA were associated with endothelial dysfunction and increased central nervous system depositions. Atherosclerotic lesion retardation was more pronounced in WTD + PSA, coinciding with higher regenerative monocyte numbers, decreased oxidative stress, and decreased inflammatory cytokines compared with WTD + PSE

Controversial role of plant sterol esters in the management of hypercholesterolaemia

Hypercholesterolaemia is a risk factor of cardiovascular diseases and is therefore a major target for primary and secondary prevention. Maintaining a healthy diet and lifestyle reduces cardiovascular risk. 'Functional foods'; supplemented with phytosterols are advertised for the management of hypercholesterolaemia and have become a widely used non-prescription approach to lower plasma cholesterol levels. It is estimated that in 2005 worldwide 3 billion US-dollars were spent on various functional foods that have regulator-approved health claims for the management of elevated cholesterol levels. In September 2000, the US Food and Drug Administration (FDA) issued an interim final rule allowing a health claim for reducing the risk of coronary heart disease for foods that contain phytosterols and are low in saturated fat and cholesterol. In fact, this was only the 12th time the FDA has authorized a health claim. The National Cholesterol Education Program Expert Panel (NCEP ATP III) recommends since 2001 phytosterol enriched functional foods as part of an optimal dietetic prevention strategy in primary and secondary prevention of cardiovascular diseases. The American Heart Association (AHA) has followed and sees phytosterols 'as a therapeutic option ... for individuals with elevated cholesterol levels';. Since then other well-esteemed societies such as the Spanish Cardiology Society, the Association of Clinical and Public Health Nutritionists in Finland, and the National Heart Foundation in Australia, to name only a few, have identified phytosterols as an important additional dietary option in the management of hypercholesterolaemia. However, recently released guidelines are more critical of food supplementation with phytosterols and draw attention to significant safety issues

Pulsed Feedback Defers Cellular Differentiation

Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable “polyphasic” positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a “timer” that operates over timescales much longer than a cell cycle

Na⁺ entry through heteromeric TRPC4/C1 channels mediates (-)Englerin A-induced cytotoxicity in synovial sarcoma cells

The sesquiterpene (-)Englerin A (EA) is an organic compound from the plant Phyllanthus engleri which acts via heteromeric TRPC4/C1 channels to cause cytotoxicity in some types of cancer cell but not normal cells. Here we identified selective cytotoxicity of EA in human synovial sarcoma cells (SW982 cells) and investigated the mechanism. EA induced cation channel current (Icat) in SW982 cells with biophysical characteristics of heteromeric TRPC4/C1 channels. Inhibitors of homomeric TRPC4 channels were weak inhibitors of the Icat and EA-induced cytotoxicity whereas a potent inhibitor of TRPC4/C1 channels (Pico145) strongly inhibited Icat and cytotoxicity. Depletion of TRPC1 converted Icat into a current with biophysical and pharmacological properties of homomeric TRPC4 channels and depletion of TRPC1 or TRPC4 suppressed the cytotoxicity of EA. A Na⁺ /K⁺-ATPase inhibitor (ouabain) potentiated EA-induced cytotoxicity and direct Na⁺ loading by gramicidin-A caused Pico145-resistant cytotoxicity in the absence of EA. We conclude that EA has a potent cytotoxic effect on human synovial sarcoma cells which is mediated by heteromeric TRPC4/C1 channels and Na⁺ loading