Bowen ratio technique

Meyers TP, Hall ME, Lindberg SE. 1996. Use of the modified Bowen ratio technique to measure fluxes of trace gases. Atmos Environ 30 3321-3329. 

Boreal zone forest stands are also part of a patchy landscape at least in terms of tree age, size, and density, which determine stand structure. More commonly, though, the stands of trees are interspersed with herbaceous and shrubby vegetation and wetlands. On average, P is found to be 0.5 mm day less than ( = 2.3 mm day ) for forests in summer. Rainfall interception has been included in this comparison because E comprised wet and dry canopy evaporation rates except for the Yakutsk study by Kelliher et al. (1997). The difference between rainfall and evaporation rates is up to 2 mm day for the two oldest studies. These studies also report by far the highest evaporation rates. These E measurements were made using the Bowen ratio technique, which is notoriously difficult to employ over forests because of the small gradients in temperature and humidity there. Except for Lalleur (1992), who also used this technique, the other measurements were made directly by eddy covariance. 

AFM allows the surface characterisation of membranes in a dry and wet state. While resolution is better than in electron microscopy, the depth of focus is much smaller. More sophisticated techniques also allow force measurements between the tip, or objects mounted on the tip, such as colloids or organics, and membranes (Bowen et al. (1998)). While some authors have successfully used AFM to show NF pores (Bowen et al (1997)) and determined their surface radius, a major drawback of the technique is that very smooth membranes are required to achieve very high resolutions and that the pore sizes determined are surface pore sizes and not the effective pore sizes required for prediction of separation. Most membranes do not meet the smooth surface criteria. Bowen et al (1997) nevertheless demonstrated successfully that some NF membranes do have distinct pores. Knoell et al (1999) used AFM to determine aspect ratios, pore perimeters, pore length and width, and the number of pores per... 

Bowen R (1991) Isotopes and Climate. London Elsevier. Brand WA (1996) High precision isotope ratio monitoring techniques in mass spectrometry. Journal of Mass... 

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