Global monitoring of wetlands--the value of ENVISAT ASAR Global mode.

This paper elaborates on recent advances in the use of ScanSAR technologies for wetland-related research. Applications of active satellite radar systems include the monitoring of inundation dynamics as well as time series analyses of surface soil wetness. For management purposes many wetlands, especially those in dry regions, need to be monitored for short and long-term changes. Another application of these technologies is monitoring the impact of climate change in permafrost transition zones where peatlands form one of the major land cover types. Therefore, examples from boreal and subtropical environments are presented using the analysed ENVISAT ASAR Global mode (GM, 1 km resolution) data acquired in 2005 and 2006. In the case of the ENVISAT ASAR instrument, data availability of the rather coarse Global Mode depends on request priorities of other competing modes, but acquisition frequency may still be on average fortnightly to monthly depending on latitude. Peatland types covering varying permafrost regimes of the West Siberian Lowlands can be distinguished from each other and other land cover by multi-temporal analyses. Up to 75% of oligotrophic bogs can be identified in the seasonal permafrost zone in both years. The high seasonal and inter-annual dynamics of the subtropic Okavango Delta can also be captured by GM time series. Response to increased precipitation in 2006 differs from flood propagation patterns. In addition, relative soil moisture maps may provide a valuable data source in order to account for external hydrological factors of such complex wetland ecosystems.

Photosynthetic properties of C4 plants growing in an African savanna/wetland mosaic.

Photosynthesis rates and photosynthesis-leaf nutrient relationships were analysed in nine tropical grass and sedge species growing in three different ecosystems: a rain-fed grassland, a seasonal floodplain, and a permanent swamp, located along a hydrological gradient in the Okavango Delta, Botswana. These investigations were conducted during the rainy season, at a time of the year when differences in growth conditions between the sites were relatively uniform. At the permanent swamp, the largest variations were found for area-based leaf nitrogen contents, from 20 mmol m(-2) to 140 mmol m(-2), nitrogen use efficiencies (NUE), from 0.2 mmol (C) mol(-1) (N) s(-1) to 2.0 mmol (C) mol(-1) (N) s(-1), and specific leaf areas (SLA), from 50 cm(2) g(-1) to 400 cm(2) g(-1). For the vegetation growing at the rain-fed grassland, the highest leaf gas exchange rates, high leaf nutrient levels, a low ratio of intercellular to ambient CO(2) concentration, and high carboxylation efficiency were found. Taken together, these observations indicate a very efficient growth strategy that is required for survival and reproduction during the relatively brief period of water availability. The overall lowest values of light-saturated photosynthesis (A(sat)) were observed at the seasonal floodplain; around 25 micromol m(-2) s(-1) and 30 micromol m(-2) s(-1). To place these observations into the broader context of functional leaf trait analysis, relationships of photosynthesis rates, specific leaf area, and foliar nutrient levels were plotted, in the same way as was done for previously published 'scaling relationships' that are based largely on C(3) plants, noting the differences in the analyses between this study and the previous study. The within- and across-species variation in both A(sat) and SLA appeared better predicted by foliar phosphorus content (dry mass or area basis) rather than by foliar nitrogen concentrations, possibly because the availability of phosphorus is even more critical than the availability of nitrogen in the studied relatively oligotrophic ecosystems.

In vivo and simulation study of artificial ventilation effects on energetic variables in cardiosurgical patients.

OBJECTIVES: The analysis of energetic ventricular variable changes during artificial ventilation, obtained by numerical simulation was done. Twenty-one sets of hemodynamic parameters for eight cardiosurgical patients were used to estimate left and right stroke work. The data were collected for three methods of ventilation: conventional, lung-protective (with minute ventilation diminished by half) and high frequency ventilation (with frequency 5, 10, or 15 Hz). METHODS: The computer simulator (CARDIOSIM) of the cardiovascular system, was used as a tool to calculate values of energetic ventricular variables for conditions that corresponded to these during in vivo measurements. Different methods of ventilation caused differences of intrathoracic pressure, haemodynamic and finally energetic ventricular variables. The trends of these variable changes were the same in in vivo and simulation studies, in the whole range of intrathoracic pressure changes (Pt = 1.5-3.5 mmHg). RESULTS: As values of main hemodynamic variables like cardiac output or arterial, systemic and pulmonary pressures were very close in both studies. Cardiac index and left ventricular stroke work also differed less than 10% for all examined patients and computer simulation. In a case of right ventricular stroke work the difference between in vivo data and simulation was a bit greater than 10% for two of eight patients under study. CONCLUSIONS: Our comparative analysis proved that numerical simulation is a very useful tool to predict changes of main hemodynamic and energy-related ventricular variables caused by different levels of positive Pt. It means that it can help an anesthesiologist to choose an appropriate method of artificial ventilation for cardiosurgical patients.

The shady side of solar protection.

OBJECTIVE: To determine the value of shade in protecting humans from solar ultraviolet (UV) radiation. DESIGN AND SETTING: Measurement with photometers of protection factors for ultraviolet B radiation (UVB) and for total solar radiation for different types of trees and other structures during the summer months (1995-1997) in south-east Queensland. (The protection ratio is the ratio of the intensity of UVB or total solar radiation in direct sunlight to that in shade.) RESULTS: For summer sun at midday, the mean (SD) UV protection ratio for the shade of trees (n = 65) was 4.21 (1.36) on a horizontal surface and 1.33 (0.30) on a vertical surface. In contrast, the mean (SD) protection ratio for total solar energy (primarily infrared) was much higher (12.1 [1.4]). Trees common in recreational areas in Australia (eucalypts: UV protection ratio, 3.52 [0.79]; Norfolk Island pines: UV protection ratio, 3.72 [0.98]) offered reduced protection compared with trees with more dense foliage (UV protection ratio, 5.48 [1.44]). Over a whole day, measurement of shade by trees and other structures showed that the UV protection ratio was lower in the morning and afternoon. Shade from awnings, buildings and hats gave similar results to those for trees. Both at midday and over a whole day satisfactory protection (UV protection ratio > 15) was obtained only in shade which eliminated exposure to the sky as well as to direct sunlight; for example, in thickly wooded areas and under low, widely overhanging structures. CONCLUSIONS: Most forms of shade, while useful, offer people insufficient protection from solar UV. A fair-skinned person sheltering under a tree could suffer sunburn after less than one hour. There is a need for appropriate design of structural shade, use of other solar protection measures in conjunction with shade, and research on behavioural responses to shade.

Generalization of induced interhemispheric interference: a chronometric approach to one-brain vs two-brains models of the hemispheres' cooperation.

A reaction time study with normal human subjects was conducted to obtain support for one or the other model of interhemispheric relations--referred to as the "one-system" and the "two-systems" hypotheses. 12 subjects were extensively trained in a complex reaction time task consisting of a "priming sub-task" which introduced interhemispheric interference and two different "test sub-tasks" measuring the generalization of interference. The interference priming produced visible slowing of RT's on subsequent trials. Interestingly, the deterioration of the two test sub-tasks was alike, despite the marked difference in the amount of the interhemispheric communication they required. This result is more in line with the one-system hypothesis, as the two-systems hypothesis predicts deterioration proportional to the amount of the required interhemispheric communication.