Crop sequence and P fertilization effects on soil P fractions under no-tillage

Nutrient Cycling in Agroecosystems - Increasing cropping intensity may affect phosphorus (P) recycling through crop residue inputs, which may differ in soils with different productivity, P...     

Competitive adsorption among sesame oil components in a concentrated miscella system

Competitive adsorption of free fatty acids and carotenoids adsorption from sesame oil miscellas on vegetable carbon was studied by regression analysis. The equations obtained indicated that unsaturated carbonyls, free fatty acids (FFA₀), and carotenoids interacted to determine fatty acid and carotenoid adsorption. The driving force for carotenoid adsorption, the carotenoid concentration (C₀), was affected by a quadratic function of free fatty acid concentration [i.e., (FFA₀/C₀)²]. As FFA₀/C₀ increased, carotenoid adsorption efficiency was reduced, possibly because the accessible adsorption sites for carotenoids were occupied by fatty acids. Unsaturated carbonyls promoted free fatty acid adsorption, probably in the pores that were readily accessible for fatty acids. However, when the carbonyl concentration increased in the oil miscella, carbonyls were adsorbed instead of fatty acids. The results indicated how different oil molecules interact and affect adsorption (i.e., free fatty acids and carotenoids). Therefore, the adsorption process of vegetable oils (i.e., bleaching) has to be considered a multicomponent adsorption system.     

Density and habitat use by the round goby (Apollonia melanostoma) in the Bay of Quinte,Lake Ontario

We assessed round goby (Apollonia melanostoma) density and size structure in two sections of the Bay of Quinte (Lake Ontario) that had been invaded by this species two years apart. Round goby density was assessed with 50 m linear transects, recorded with an underwater video recording apparatus developed for this study that included a depth sounder for maintaining a fixed distance above the substrate. The highest mean round goby densities were observed in the shallowest depth zone (1.5–3 m) at both sites, but there were differences between the sites in the habitat types where the highest densities occurred and there were no significant density differences among habitat types at either site (rock with sparse vegetation, mud with sparse vegetation, sand/mud with moderate vegetation cover). In the upper bay, mean body length of round gobies declined with depth, whereas in the lower bay, mean round goby length was greatest in the deepest zone. Mean body length of round gobies did not differ significantly by habitat type in either section of the bay.     

He(1s) angular distributions simulations for He(1s) on Al(1 1 1) collisions in the keV energy range at grazing incidences

We have calculated charge fractions and angular distributions of scattered He atoms resulting from the interaction of keV He⁺ beams at grazing incidences with an Al(1 1 1) surface. Several improvements over our earlier approaches have been incorporated. These are a more sophisticated RPA image potential for the ion-metal interaction as well as kinematic factors affecting the static rates for the Auger transfer mechanisms. For interaction cases in which both perpendicular and parallel velocities are low, we obtain angular distributions which have a better agreement with the experimental data than our earlier version of the theory, although still the theoretical results do not reach total neutralization of the beam as the experimental results show.     

Phytoplankton dynamics in two tropical rivers with different degrees of human impact (southeast Brazil)

Potamoplankton attracts little research attention worldwide and this also holds true in Brazil, despite its numerous river systems. The origin and maintenance of phytoplankton populations in these systems have not been well studied. We analysed biological, physical and chemical parameters of the Paraibuna and Pomba rivers to identify the main driving forces behind temporal and spatial phytoplankton patterns. Both systems are located in the southeast, the most populated region. These rivers are similar in climate and geomorphology, and have become eutrophic due to the increase in the human population of the region, especially in Paraibuna River catchments. Twelve and eleven stations were, respectively, sampled during the dry and rainy seasons in the Paraibuna and Pomba rivers. The seasonal pattern of abiotic and biotic variables was related to the increase in the discharge and dilution caused by the rainy period. However, human influences such as the presence of a reservoir and sewage inflow were important to distinguish the rivers. The phytoplankton community of Paraibuna River was influenced by Chapéu D'Uvas Reservoir, which was dominated by a toxic population of Cylindrospermopsis raciborskii. Pomba River phytoplankton was typical of the lotic tropical systems. Phytoplankton functional groups in both rivers were those commonly found in turbid and turbulent shallow lakes. Although the functional group approach was originally described for lentic environments, our data support this approach for lotic community patterns. Copyright © 2007 John Wiley & Sons, Ltd.     

Perceptual adaptive insensitivity for support vector machine image coding

Support vector machine (SVM) learning has been recently proposed for image compression in the frequency domain using a constant /spl epsiv/-insensitivity zone by Robinson and Kecman. However, according to the statistical properties of natural images and the properties of human perception, a constant insensitivity makes sense in the spatial domain but it is certainly not a good option in a frequency domain. In fact, in their approach, they made a fixed low-pass assumption as the number of discrete cosine transform (DCT) coefficients to be used in the training was limited. This paper extends the work of Robinson and Kecman by proposing the use of adaptive insensitivity SVMs for image coding using an appropriate distortion criterion , based on a simple visual cortex model. Training the SVM by using an accurate perception model avoids any a priori assumption and improves the rate-distortion performance of the original approach.     

Fatal myelofibrosis following fludarabine administration in a patient with indolent lymphoma

We report a case of fulminant myelofibrosis after administration of fludarabine in a patient diagnosed as having refractory low-grade lymphoma, progressing fatally. Myelofibrosis in the setting of an indolent lymphoma is very rare; this fact, and the short period between drug administration and fibrosis suggest an etiopathogenic link, although this potential and severe adverse effect of fludarabine has not been previously reported in the literature.