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The hydration of a variety of phospholipids has been studied, gravimetrically. The water adsorption isotherms obtained have been analyzed by the use of BET methodology. The major findings are as follows: Phospholipids containing choline, as part of their head group and having a glycerol backbone are „strong” water adsorbers; the nature and fluidity of the hydrocarbon chains do not control the „strong” vs „weak” nature of the water binding but do modulate the amount of adsorbed water. The number of methyl groups present on the N+ moiety of the head groups determines both the nature of the water binding as well as the amount of water adsorbed. The electrical charge on the phospholipid head group does not, in itself, determine the nature of the water binding; it does, however affect the amount of water bound. All of the phospholipids studied exhibit a very rapid rise in electrical conductivity as water is adsorbed; this rise reaches a limiting saturation value at or close to fnat for the completion of the first monolayer of water adsorbed. These findings are discussed in terms of the molecular structure of the phospholipids.
Total body electrical conductivity (TOBEC) is a method for non-destructively esti­mating body composition. We sought to monitor seasonal changes in total body fat in northern red-backed voles Clethrionomys rutilus (Pallas, 1779), a microtine (10-45 g). We validated two new TOBEC instruments: the SA-3000 by EM-SCAN Inc. and the ACAN-2 by Jagmar Inc. Both instruments explained 94% of the variation in lean body mass and total body water. However, accuracy of fat estimates generated from lean mass predictions was poor for both instruments (± > 100%). Two instrument-specific multiple regression models and a TOBEC-free multiple regression model were used to estimate total body fat. All three improved the ability to predict total body fat in C, rutilus. These two TOBEC instruments can not be used to measure changes in total body fat of individual C. rutilus due to the small amount of fat reserves and lack of seasonal variation.
Cocoa remains in the same field for decades, resulting in plantations dominated with aging trees growing on variable and depleted soils. We determined the spatio-temporal variability of key soil properties in a (5.81 ha) field from the International Cocoa Genebank, Trinidad using geophysical methods. Multi-year (2008-2009) measurements of apparent electrical conductivity at 0-0.75 m (shallow) and 0.75-1.5 m (deep) were conducted. Apparent electrical conductivity at deep and shallow gave the strongest linear correlation with clay-silt content (R = 0.67 and R = 0.78, respectively) and soil solution electrical conductivity (R = 0.76 and R = 0.60, respectively). Spearman rank correlation coefficients ranged between 0.89-0.97 and 0.81-0.95 for apparent electrical conductivity at deep and shallow, respectively, signifying a strong linear dependence between measurement days. Thus, in the humid tropics, cocoa fields with thick organic litter layer and relatively dense understory cover, experience minimal fluctuations in transient properties of soil water and temperature at the topsoil resulting in similarly stable apparent electrical conductivity at shallow and deep. Therefore, apparent electrical conductivity at shallow, which covers the depth where cocoa feeder roots concentrate, can be used as a fertility indicator and to develop soil zones for efficient application of inputs and management of cocoa fields.
Bat researchers have used both morphological indices and total body electric conductivity (TOBEC) as proxies for body condition in a variety of studies, but have typically not validated these indices against direct measurement of body composition. We quantified body composition (total carcass lipids) to determine if morphological indices were useful predictors of body condition in big brown bats (Eptesicus fuscus). We also evaluated body composition indirectly by TOBEC using EM-SCAN® technology. The most important predictors of body composition in multiple regression analysis were body mass-to-forearm ratio (partial r2 = 0.82, P < 0.001) followed by TOBEC measurement (partial r2 = 0.08, P < 0.001) and to a minor extent head length (partial r2 = 0.02, P < 0.05). Morphological condition indices alone may be adequate for some studies because of lower cost and effort. Marking bats with passive integrated transponder (PIT) tags affected TOBEC measurements.
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