Hypoxia reduces the effect of photoreceptor bleaching.

Hypoxia and light illumination can both decrease oxygen consumption in the photoreceptor layers. The purpose of the present study was to investigate whether the mutual effects of hypoxia and intense illumination to the photoreceptors are additive. The a-wave of flash electroretinogram (fERG) was recorded to indirectly measure the photoreceptors function under given conditions. Six normal healthy subjects, mean age 34.0 ± 3.8 years, all of whom had high-altitude (>3,000 m) mountain hiking experience, were recruited for the study. Flash a-wave electroretinography was examined under four conditions: (1) normal (D/N); (2) systemic hypoxia induced by inhaling a mixture of O(2) and N(2) gases, which caused oxyhemoglobin saturation (SaO(2)) ≈ 80% (D/H); (3) intense light illumination, which resulted in photoreceptor bleaching (B/N); and (4) a combination of conditions b and c (B/H). Thirty light stimuli, each with a 20-ms ON and 1,980-ms OFF cycle, were given and ERG performed to probe the photoreceptor function. The results showed that a-wave at the various conditions did not respond to all stimuli. The average a-wave amplitudes were 91.4 ± 46.5, 22.8 ± 42.5, 15.5 ± 28.9, and 35.2 ± 41.1 µV for D/N, D/H, B/N, and B/H, respectively. Nonparametric Friedman test for a-wave amplitude indicated that significant differences occurred in D/N-D/H, D/N-B/N, D/N-B/H, D/H-B/H, and B/N-B/H (all p values were <0.001, but D/H-B/N was 0.264). Thus, systemic hypoxia or strong illumination to the retina can cause an absence of the ERG a-wave or change its response, although individual differences were observed. In this study, systemic hypoxia appeared to reduce photoreceptor bleaching, an interesting finding in itself. The mechanisms underlying the disappearance of the ERG a-wave following hypoxia or intense illumination to the photoreceptors seem to differ.

Characterizing hydrochemical properties of springs in Taiwan based on their geological origins.

This study was performed to characterize hydrochemical properties of springs based on their geological origins in Taiwan. Stepwise discriminant analysis (DA) was used to establish a linear classification model of springs using hydrochemical parameters. Two hydrochemical datasets-ion concentrations and relative proportions of equivalents per liter of major ions-were included to perform prediction of the geological origins of springs. Analyzed results reveal that DA using relative proportions of equivalents per liter of major ions yields a 95.6% right assignation, which is superior to DA using ion concentrations. This result indicates that relative proportions of equivalents of major hydrochemical parameters in spring water are more highly associated with the geological origins than ion concentrations do. Low percentages of Na(+) equivalents are common properties of springs emerging from acid-sulfate and neutral-sulfate igneous rock. Springs emerging from metamorphic rock show low percentages of Cl( - ) equivalents and high percentages of HCO[Formula: see text] equivalents, and springs emerging from sedimentary rock exhibit high Cl( - )/SO(2-)(4) ratios.

Mapping and assessing spatial multiscale variations of birds associated with urban environments in metropolitan Taipei, Taiwan.

Environmental change can be monitored and assessed by analyzing changes in bird populations. This study employed multivariate factorial kriging (MFK) to determine the multiscale changes in the distribution of five commonly observed bird species to urban environmental change. Areas of metropolitan Taipei were analyzed to determine the extent and effect of land cover. A digital elevation model and normalized difference vegetation index were also constructed. Spatial patterns of variation in bird populations were analyzed by MFK at a regional scale (16 km) and local scale (2 km). Comparison of MFK results with those obtained by conventional principal component analysis (PCA) and correspondence analysis (CA) showed that the conventional PCA results were comparable to the MFK results at the local scale, and the CA results were comparable to MFK results at the regional scale. The MFK indicated that local-scale variation accounts for a larger proportion of the total variation than regional-scale variation, and local-scale variation is affected by more factors than regional scale variation. The MFK results also showed that heterogeneous elevation exerts a geographical influence on bird populations at the regional scale whereas the land cover of urban meadows in densely populated urban areas of Taipei exerts a local influence. The suburban trees and meadows in belt regions between suburbs have local and regional influences on bird distributions, respectively. The spatial patterns of bird populations in response to urban environments can be adequately explained by their diet categories and body sizes. The MFK, which simultaneously provides descriptive variations and spatial patterns in species at determinate scales, facilitates environmental interpretations of ordination results and identification of determinants for conservation efforts at multiple scales.

Monitoring and Predicting Land-use Changes and the Hydrology of the Urbanized Paochiao Watershed in Taiwan Using Remote Sensing Data, Urban Growth Models and a Hydrological Model.

Monitoring and simulating urban sprawl and its effects on land-use patterns andhydrological processes in urbanized watersheds are essential in land-use and waterresourceplanning and management. This study applies a novel framework to the urbangrowth model Slope, Land use, Excluded land, Urban extent, Transportation, andHillshading (SLEUTH) and land-use change with the Conversion of Land use and itsEffects (CLUE-s) model using historical SPOT images to predict urban sprawl in thePaochiao watershed in Taipei County, Taiwan. The historical and predicted land-use datawas input into Patch Analyst to obtain landscape metrics. This data was also input to theGeneralized Watershed Loading Function (GWLF) model to analyze the effects of futureurban sprawl on the land-use patterns and watershed hydrology. The landscape metrics ofthe historical SPOT images show that land-use patterns changed between 1990-2000. TheSLEUTH model accurately simulated historical land-use patterns and urban sprawl in thePaochiao watershed, and simulated future clustered land-use patterns (2001-2025). TheCLUE-s model also simulated land-use patterns for the same period and yielded historical trends in the metrics of land-use patterns. The land-use patterns predicted by the SLEUTHand CLUE-s models show the significant impact urban sprawl will have on land-usepatterns in the Paochiao watershed. The historical and predicted land-use patterns in thewatershed tended to fragment, had regular shapes and interspersion patterns, but wererelatively less isolated in 2001-2025 and less interspersed from 2005-2025 compared withland-use pattern in 1990. During the study, the variability and magnitude of hydrologicalcomponents based on the historical and predicted land-use patterns were cumulativelyaffected by urban sprawl in the watershed; specifically, surface runoff increasedsignificantly by 22.0% and baseflow decreased by 18.0% during 1990-2025. The proposedapproach is an effective means of enhancing land-use monitoring and management ofurbanized watersheds.

Integrating Remote Sensing Data with Directional Two- Dimensional Wavelet Analysis and Open Geospatial Techniques for Efficient Disaster Monitoring and Management.

In Taiwan, earthquakes have long been recognized as a major cause oflandslides that are wide spread by floods brought by typhoons followed. Distinguishingbetween landslide spatial patterns in different disturbance regimes is fundamental fordisaster monitoring, management, and land-cover restoration. To circumscribe landslides,this study adopts the normalized difference vegetation index (NDVI), which can bedetermined by simply applying mathematical operations of near-infrared and visible-redspectral data immediately after remotely sensed data is acquired. In real-time disastermonitoring, the NDVI is more effective than using land-cover classifications generatedfrom remotely sensed data as land-cover classification tasks are extremely time consuming.Directional two-dimensional (2D) wavelet analysis has an advantage over traditionalspectrum analysis in that it determines localized variations along a specific direction whenidentifying dominant modes of change, and where those modes are located in multi-temporal remotely sensed images. Open geospatial techniques comprise a series ofsolutions developed based on Open Geospatial Consortium specifications that can beapplied to encode data for interoperability and develop an open geospatial service for sharing data. This study presents a novel approach and framework that uses directional 2Dwavelet analysis of real-time NDVI images to effectively identify landslide patterns andshare resulting patterns via open geospatial techniques. As a case study, this study analyzedNDVI images derived from SPOT HRV images before and after the ChiChi earthquake(7.3 on the Richter scale) that hit the Chenyulan basin in Taiwan, as well as images aftertwo large typhoons (Xangsane and Toraji) to delineate the spatial patterns of landslidescaused by major disturbances. Disturbed spatial patterns of landslides that followed theseevents were successfully delineated using 2D wavelet analysis, and results of patternrecognitions of landslides were distributed simultaneously to other agents using geographymarkup language. Real-time information allows successive platforms (agents) to work withlocal geospatial data for disaster management. Furthermore, the proposed is suitable fordetecting landslides in various regions on continental, regional, and local scales usingremotely sensed data in various resolutions derived from SPOT HRV, IKONOS, andQuickBird multispectral images.

Mapping of spatial multi-scale sources of arsenic variation in groundwater on ChiaNan floodplain of Taiwan.

This study applied multivariate factorial kriging to derive the characteristics of the spatial variations of groundwater arsenic distributions at different scales on the ChiaNan floodplain, Taiwan. Seven variables (dissolved oxygen, oxidation-reduction potential, alkalinity, sulfate, iron cations, manganese cations and total organic carbon) and Arsenic were adopted to analyze the mechanisms of arsenic enrichments in groundwater. The hydrogeological environment had spatial and quantitative influences on arsenic enrichments at different scales. The regional scale was set to 32 km referring to the extension distance of flow paths to reflect the effects of flushing in the aquifer, while the local scale was set to 16 km referring to the farthest distance of seawater intrusion to determine the influence of seawater intrusion. The results of factorial kriging suggested that arsenic releases resulted partially from pyrite oxidation during the flushing at the regional scale and partially due to the siderite dissolution at the local scale. Overall, the alkalinity dominated arsenic distribution in groundwater at both the regional and local scales. The multivariate factorial kriging results also demonstrated that seawater intrusion slightly affected the increase of arsenic in groundwater, accounting for only 17.3% of total variation. However, the interaction of seawater intrusion and arsenic distribution in space indicated that seawater intrusion restrained the distribution of arsenic from the areas where seawater was located. High dissolved oxygen was found at where over-pumping induced drawdown cones occurred and also limited the spatial variation of arsenic. Our findings indicate that multivariate factorial kriging can be a useful mapping tool to improve understanding of the mechanism of arsenic release in groundwater at different scales. And the results conducted from the application of multivariate factorial kriging in southwestern Taiwan reveal the important influences of the hydrogeological processes, either artificial or natural, on the arsenic variations in groundwater.