Effects of selective excitotoxic lesions of the nucleus accumbens core, anterior cingulate cortex, and central nucleus of the amygdala on autoshaping performance in rats.

The nucleus accumbens core (AcbC), anterior cingulate cortex (ACC), and central nucleus of the amygdala (CeA) are required for normal acquisition of tasks based on stimulus-reward associations. However, it is not known whether they are involved purely in the learning process or are required for behavioral expression of a learned response. Rats were trained preoperatively on a Pavlovian autoshaping task in which pairing a visual conditioned stimulus (CS+) with food causes subjects to approach the CS+ while not approaching an impaired stimulus (CS-). Subjects then received lesions of the AcbC, ACC, or CeA before being retested. AcbC lesions severely impaired performance; lesioned subjects approached the CS + significantly less often than controls, failing to discriminate between the CS + and CS-. ACC lesions also impaired performance but did not abolish discrimination entirely. CeA lesions had no effect on performance. Thus, the CeA is required for learning, but not expression, of a conditioned approach response, implying that it makes a specific contribution to the learning of stimulus-reward associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis of block copolymers based on oxyethylene chains and their use as polymer electrolytes

High-molecular-weight copolymers were prepared consisting predominantly of oxyethylene and oxymethylene-oligo(oxyethylene) blocks with a small 1-phenylethylene block. Ionic conductivities of mixtures of the copolymers with CF₃SO₃Li were measured.     

Rates of Trace Mineral-Catalyzed Decomposition of Hydrogen Peroxide

Rapid hydrogen peroxide (H2O2) decomposition is a significant limitation of catalyzed H2O2 propagations (i.e., modified Fenton’s reagent) for the remediation of contaminated soil and groundwater by in situ chemical oxidation. Rates of H2O2 decomposition mediated by seven trace minerals and four iron and manganese oxides were evaluated in batch reactors containing slurries of H2O2 and each of 11 minerals. At pH 3, the dominant catalysts in the decomposition of H2O2 on a per surface area basis were the manganese and iron oxides pyrolusite, goethite, and hematite, while decomposition rates in the presence of the manganese oxyhydroxide manganite and the trace mineral siderite were one to two orders of magnitude lower. At pH 7, the dominant catalysts were hematite and pyrolusite, and decomposition rates were one to two orders of magnitude lower in the presence of goethite, manganite, and siderite. The trace minerals anatase, bauxite, cuprite, ilmenite, magnesite, and willemite provided the least activity for decomposing H2O2 at both pH regimes. The results of this study document that the trace minerals anatase, bauxite, cuprite, ilmenite, magnesite, siderite, and willemite do not provide a significant pathway for H2O2 decomposition in the subsurface, and efforts to stabilize H2O2 for ISCO should focus on reactions occurring on the surfaces of iron and manganese oxides.     

Short-term retention of location within a homogeneous behavior sequence in rats.

Fed 8 male Sprague-Dawley rats for entering a food tray following 12 or more consecutive lever presses. Short-term retention of location within the 12-press requirement was then tested by interrupting the press sequence with time-outs (TOs) after various numbers of presses. Each sequence contained 1 TO, and the duration of the TO was varied (0-16 sec) across phases of the experiment. As TO duration increased, the number of presses per trial went from being independent of TO location to being directly related to it. Derived retention scores showed a very rapid negatively accelerated, decreasing relationship to TO duration. Limitations on the interpretation of these retention functions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attenuation and depolarisation data obtained on 12 GHz satellite-Earth paths at four Canadian locations

A preliminary result of the Communication Technology Satellite (CTS) propagation experiment carried out in Canada is presented. These results of 11.7 GHz band were obtained in 1978 while the CTS was located at 116 degrees W longitude.     

Electron-transfer coupling in microbial fuel cells. 2. performance of fuel cells containing selected microorganism—mediator—substrate combinations

Various phenoxazine, phenothiazine, phenazine, indophenol and bipyridilium derivatives were tested for their effectiveness as redox mediators in microbial fuel cells containing Alcaligenes eutrophus, Bacillus subtilis, Escherichia coli, or Proteus vulgaris as the active biological agent, and glucose or succinate as the oxidisable substrate. A ferricyanide-Pt cathode was used. The open-circuit cell e.m.f.′s increased in the order of increasing negative formal redox potentials at pH 7(E⁷_m) of the redox compounds. Several of the redox agents worked well as mediators, maintaining steady currents over several hours, and thionine was found to be particularly effective in maintaining relatively high cell voltages when current was drawn from the cell. A number of the compounds tested did not function well, either because they were incompletely or slowly reduced by the microorganisms or because of their instability. P. vulgaris, with thionine as mediator and glucose as substrate, showed the best performance in a fuel cell. This system was examined in some detail under various conditions of external load to establish the effects of organism concentration, mediator concentration, and substrate addition. Coulombic outputs from these cells were calculated by integration of the current-time plots. Coulombic yields of 30–60% were obtained, on the basis of (theoretical) complete oxidation of added substrate to CO₂ and water.     

Ionic membranes for water desalination. I. Charge mosaic membranes from blends of random copolymers

The incompatibility of polymers was used in order to prepare films with regular phase separation. The conversion of the separate phases into polyelectrolytes of different charge should lead to the preparation of charge mosaic membranes for piezodialysis. Copolymers of suitable monomers with 20–45 mole-% butadiene content were synthesized which could be cross-linked with sulfur monochloride. The comonomers were: styrene, 2-vinyl pyridine, 4-vinyl pyridine, methacrylic acid, methyl methacrylate and 2-chloroethyl methacrylate. After conversion into the ionic form cross-linked films of these copolymers showed salt rejections in the range of 26–78 % and water permeabilities of 40–43 [1· mm· m^?2· day^?1], respectively. These films can be used as anion and cation exchange membranes for water desalination. Mixtures of poly (2-vinyl pyridine-co-butadiene) and poly (styrene-co-butadiene) yielded films with regular phase separation. After cross-linking and conversion into the ionic form these charge mosaic membranes were porous and had poor mechanical strength. Despite these unfavourable properties a salt enrichment of 4.8 % was found in one case.     

Potential and limitations of Sr/Ca ratios in coccolith carbonate: new perspectives from cultures and monospecific samples from sediments

The Sr/Ca ratio of coccoliths was recently proposed as a potential indicator of past growth rates of coccolithophorids, marine algae, which play key roles in both the global carbonate and carbon cycles. We synthesize calibrations of this proxy through laboratory culture studies and analysis of monospecific coccolith assemblages from surface sediments. Cultures of coccolithophorids Helicosphaera carteri, Syracosphaera pulchra and Algirospira robusta confirm a 1-2% increase in Sr/Ca per degrees C previously identified in Emiliania huxleyi and Gephyrocapsa oceanica. This effect is not due merely to increases in growth rate with temperature and must be considered in palaeoceanographic studies. In light-limited cultures of E. huxleyi, Calcidiscus leptoporus and G. oceanica at constant temperature, coccolith Sr/Ca ratios vary by 10% across the range of possible growth and calcification rates for a given species. Among different species under similar culture conditions, Sr/Ca ratios vary by 30%. Although the highest ratios are in the cells with highest calcification and organic carbon fixation rates, at lower rates there is much scatter, indicating that different mechanisms control interspecific and intraspecific coccolith Sr/Ca variations. In field studies in the Equatorial Pacific and Somalia coastal region, coccolith Sr/Ca correlates with upwelling intensity and productivity. A more dynamic response is observed in larger coccoliths like C. leptoporus (23-55% variation in Sr/Ca) than in smaller coccoliths of G. oceanica or Florisphaera profunda (6-15% variation in Sr/Ca). This response suggests that, despite temperature effects, coccolith Sr/Ca has potential as an indicator of coccolithophorid productivity. If the variable Sr/Ca response of different species accurately reflects their variable productivity response to upwelling (and not different slopes of Sr/Ca with productivity), coccolith Sr/Ca could provide useful data on past changes in coccolith ecology. The mechanism of coccolith Sr/Ca variations remains poorly understood but is probably more closely tied to biochemical cycles during carbon acquisition than to chemical kinetic effects on Sr incorporation in the calcite coccolith crystals.