High nutrient loading and climatic parameters influence the dominance and dissimilarity of toxigenic cyanobacteria in northern bays of Lake Victoria

Eutrophication of Lake Victoria led to changes in its phytoplankton communities. However, different levels of eutrophication exist in the open lake and the bays, and between embayments. This study utilized spatial and temporal sampling of Napoleon Gulf and Murchison Bay, exhibiting different trophic conditions. Over one year, we investigated phytoplankton biomass, richness, diversity and dissimilarity, and related the dynamics of the dominant species to the limnological and climatic conditions. The results confirmed that Napoleon Gulf and Murchison Bay showed large differences in eutrophication status, with lower nutrient concentrations in Napoleon Gulf than in Murchison Bay, where a strong gradient was observed from inshore to offshore areas. These nutrient dynamics resulted in a 4 to 10 fold higher chlorophyll-a in Murchison Bay than in Napoleon Gulf. From the embayments, 135 phytoplankton taxa were recorded with no significant differences in alpha diversity. However, high dissimilarity in community structure was observed in beta diversity, mostly due to a turnover among the dominant toxigenic species. Thus, from a similar species pool, there was a shift in the dominant toxigenic cyanobacteria from Microcystis flos-aquae and M. aeruginosa in Murchison Bay, Dolichospermum circinale and Planktolyngbya circumcreta in Napoleon Gulf to D. circinale in the offshore stations. These cyanobacteria are toxigenic taxa with known health hazards. Using partial least square models, we showed that both climatic variables (e.g. wind, solar radiation) and levels of inorganic dissolved nutrients (e.g. SRP, NO₃^–, and NH₄⁺) are the main drivers of differences and dominance in cyanobacteria communities in northern Lake Victoria.     

Dual diagnosis: a treatment model for substance abuse and major mental illness

The treatment of "dual diagnosis", co-occurring substance abuse and mental illness, calls for addressing two serious and often confounding problems. The authors introduce an expanded version of the transtheoretical model of change as formulated by J.O. Prochaska and C.C. DiClemente, and suggest that this new version offers a pragmatic approach to the conceptualization and treatment of dual diagnosis. The potential utility of the treatment model is presented through the authors' experiences in working with inner-city, chronic mentally ill individuals with substance abuse problems. Practical guidelines for dual diagnosis group therapy are discussed.     

Bioinspired Visuomotor Convergence

In this paper, wide-field integration methods, which are inspired by the spatial decompositions of wide-field patterns of optic flow in the insect visuomotor system, are explored as an efficient means to extract visual cues for guidance and navigation. A control-theoretic framework is developed and used to quantitatively link weighting functions to behaviorally-relevant interpretations such as relative orientation, position, and speed in a corridor environment. It is shown through analysis and demonstration on a ground vehicle that the proposed sensorimotor architecture gives rise to navigational heuristics, namely, centering and speed regulation, which are observed in natural systems.      

Implementation of wide-field integration of optic flow for autonomous quadrotor navigation

Insects are capable of robust visual navigation in complex environments using efficient information extraction and processing approaches. This paper presents an implementation of insect inspired visual navigation that uses spatial decompositions of the instantaneous optic flow to extract local proximity information. The approach is demonstrated in a corridor environment on an autonomous quadrotor micro-air-vehicle (MAV) where all the sensing and processing, including altitude, attitude, and outer loop control is performed on-board. The resulting methodology has the advantages of computation speed and simplicity, hence are consistent with the stringent size, weight, and power requirements of MAVs.     

Performance of selected anion exchange resins for the treatment of a high DOC content surface water

The objective of this study was first to compare the performance of four strong anion exchange resins (AERs) (MIEX from Orica Pty Ltd, DOWEX-11 and DOWEX-MSA from DOW chemical and IRA-938 from Rohm and Haas) for their application in drinking water treatment (natural organic matter (NOM), mineral anions (nitrate, sulfate and bromide) and pesticide removal) using bench-scale experimental procedures on a high DOC content surface water. The efficiency of MIEX for NOM and mineral anions removal was furthermore evaluated using bench-scale dose-response experiments on raw, clarified and post-ozonated waters. NOM removal was assessed using the measurement of dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254) and the use of high-performance size exclusion chromatography with UV (HPSEC/UV) and fluorescence detection (HPSEC/FLUO). The MIEX and IRA938 anionic resins exhibit a faster removal of NOM and mineral anions compared to the DOWEX11 and MSA AERs. All the resins were found to be very effective with similar performances after 30 to 45 min of contact time. As expected, only limited sorption of atrazine and isoproturon (C0=1 microg/L) occurred with MIEX, DOWEX11 and MSA AERs. MIEX resin proved to be very efficient in eliminating NOM of high-molecular weight but also a large part of the smallest UV absorbing organic compounds which were refractory to coagulation/flocculation treatment. Remaining DOC levels after 30 min of contact with MIEX were found similar in raw water, clarified water and even post-ozonated water implying no DOC benefit can be gained by employing conventional treatment prior to MIEX treatment. Removal of bromide (initial concentration 110 microg/L) was also observed and ranged from 30% to 65% for resin dose increasing from 2 to 8 mL/L. T     

Viscoelastic properties of oil-water interfaces covered by bovine beta-casein tryptic peptides

A combination of proteolysis and dilational rheology has been used to study the behavior of films of beta-casein (beta-CN) and of peptides spread at the oil-water interface. Identification of the peptides produced by trypsin hydrolysis of beta-CN in emulsion at 37 degrees C provided information on the structure of beta-CN adsorbed at the oil-water interface. Good interface properties were observed for beta-CN or its peptides, probably because of the amphipathic nature of beta-CN or a synergistic effect between hydrophilic and hydrophobic peptides. Remarkable surface activity was found for the amphipathic peptide beta-CN (f114-169). Rheological studies had shown that interface films made with peptide fractions or with beta-CN were elastic rather than viscous. Film made with the purified peptide beta-CN (f114-169) was merely elastic at the triolein-water interface. A decrease of the viscoelastic modulus was observed for aging beta-CN film but not for aging peptide films; The beta-CN decrease was related to the flexibility of its structure. When the interface is increased by the dilation of an aqueous droplet plunged into oil, beta-CN may expose new polypeptide trains to cover the increased interface, unlike peptides with simpler structures.