Infectious ideas: Modelling the diffusion of ideas across social networks

Will the practice of collecting wild honey wearing no clothes become a widespread practice in Zimbabwe? Or will beekeeping take over as the main way that people acquire honey? Both practices impact on forest resources; how can the foresters influence the uptake of these ideas? This paper describes an exploratory modelling study investigating how social network patterns affect the way ideas spread around communities. It concludes that increasing the density of social networks increases the spread of successful ideas whilst speeding the loss of ideas with no competitive advantage. Some different kinds of competitive advantage are explored in the context of forest management and rural extension.     

Characterization of CIMMYT bread wheats for high- and low-molecular weight glutenin subunits and other quality-related genes with SDS-PAGE,RP-HPLC and molecular markers

Two hundred and seventy-three CIMMYT bread wheat cultivars and advanced lines grown under irrigated conditions in Mexico during the 2005-06 Yaqui crop cycle were characterized for quality-related genetic traits using gene-specific markers for some high- and low-molecular-weight glutenin subunit (HMW-GS and LMW-GS) genes, polyphenol oxidase (PPO), phytoene synthase (PSY), and waxy genes. Of them, 142 were analyzed for quality parameters including SDS sedimentation volume (SDS-SV), dough mixing time, and Alveograph parameters, and for HMW-GS and LMW-GS compositions using sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and reversed-phase high-performance liquid chromatography (RP-HPLC). For the Ppo-A1 locus tested with the marker PPO18, the frequencies of alleles Ppo-A1a and Ppo-A1b were 79.1 and 20.2%, respectively, and no PCR fragment was amplified in 2 lines (0.73%), whereas 227 lines (83.2%) contained the allele Ppo-D1a and 46 lines (16.8%) had Ppo-D1b detected by markers PPO16 and PPO29. For the marker YP7A, 142 lines (52.0%) were assumed to have the allele Psy-A1a and 131 lines (48.0%) contained the allele Psy-A1b. In the case of the marker YP7B for the gene Psy-B1, the alleles Psy-B1a and Psy-B1b were detected in 155 (56.8%) and 43 (15.8%) lines, respectively, and 75 (27.4%) lines possessed the allele Psy-B1d detected by the marker YP7B-3. All 273 lines contained the alleles Wx-A1a and Wx-D1a as determined by markers MAG264 and MAG269, respectively. Using the marker Wx-B1, 204 lines (74.7%) were presumed to have the Wx-B1a allele and 69 (25.3%) possessed Wx-B1b. The over-expressing allele of Bx7 ^OE and subunit By8*, not clearly seen with SDS-PAGE, were detected by RP-HPLC. The numbers of lines with subunits Ax2*, By8, By9, Bx17, Bx20, Dx5, and Glu-B3j were 90, 16, 57, 5, 46, 118, and 33, respectively, in the 142 lines analyzed with molecular markers, and were consistent with the results obtained by SDS-PAGE, except for one line with the 1A.1R translocation. Subunits Ax1 and Ax2* at the Glu-A1 locus showed significantly better effects on all quality parameters than subunit Null. Subunits 5 + 10 gave significantly better effects for all parameters. Subunit Glu-A3b showed more positive effects than its alternative alleles on SDS-SV and SDS-sedimentation volume/protein content index (SPI). The allele Glu-B3g showed the best effect on SDS-SV and Alveograph W, whereas Glu-B3j, associated with the 1B.1R translocation, exhibited a strongly negative effect on all quality parameters.     

Changes in Certain Antioxidative Enzymes and Growth Parameters as a Result of Complete Submergence and Subsequent Re-aeration of Rice Cultivars Differing in Submergence Tolerance

An experiment was conducted on the three indica rice ( Oryza sativa L.) cultivars IR 42, CR 383-10 and FR 13A, which are susceptible to submergence, submergence-avoiding and tolerant to submergence, respectively. A deleterious effect of submergence was noted as both above-ground dry matter accumulation and chlorophyll content decreased during submergence and subsequent re-aeration. However, the rate of reduction was lower in the tolerant cultivar. The tolerant cultivar FR 13A maintained higher dry weight during submergence and subsequent re-aeration and accumulated lower proline and malondialdehyde contents than the other cultivars. The activities of the enzymes catalase, peroxidase and superoxide dismutase, expressed on a per g fresh weight of leaves basis, were higher in FR 13A than in the other cultivars, both under water and 24 h after the initiation of re-aeration. However, ascorbic acid oxidase activity was lower in FR 13A. The cultivar CR 383-10, which has the capacity to accumulate more above-ground dry matter under normal conditions, showed a greater elongation ability under submergence and was similar to the susceptible cultivar IR 42 in terms of enzyme activities and the other parameters investigated during submergence and subsequent re-aeration.     

Molecular characterization of chromium (VI) reducing potential in Gram positive bacteria isolated from contaminated sites

Hexavalent chromium [Cr(VI)] is highly toxic, teratogenic and carcinogenic to man and other animals. Some bacterial species have the ability to reduce Cr(VI) to a stable speciation state of trivalent chromium [Cr(III)], which is insoluble and comparatively less toxic. Therefore, the reduction of Cr(VI) thus provides potential as a means for environmental bioremediation of Cr(VI) pollution. In the present study bacteria isolated from chromium and diesel contaminated sites were found to have the ability to rapidly reduce highly toxic concentrations of Cr(VI) to Cr(III) when grown in minimal medium supplemented with glucose as the sole carbon source. Partial chromate reductase gene sequences were retrieved after PCR amplification of genomic DNA extracted from three Gram positive isolates which were highly similar (>99% sequence similarity) to chromate reductase genes found in Gram negative bacteria, more specifically those identified from Escherichia coli and Shigella spp. whole-genome studies. The isolated bacteria were putatively identified by 16S rRNA gene sequencing as Arthrobacter aurescens strain MM10, Bacillus atrophaeus strain MM20, and Rhodococcus erythropolis strain MM30.     

Ultrasonic Enhanced Desorption of DDT from Contaminated Soils

In this study, using high-power low-frequency ultrasound, heated slurries with anionic surfactant sodium dodecyl sulfate (SDS) were treated to enhance desorption of DDT from soils with high clay, silt, and organic matter content and different pH (5.6?C8.4). The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20 wt.% were studied. For a soil slurry (10 wt.%) at pH 6.9 with 0.1% v/v SDS surfactant heated to 40°C for 30 min, desorption was above 80% in 30 s using 20 kHz, 932 W/L ultrasonic intensity without solvent extraction. Other soils gave lower desorption efficiency in the range 40?C60% after 30 s ultrasonic treatment. The percentage of organic matter, dissolved organic carbon, soil surface area, clay and silt percentage, and soil pH level were the key parameters influencing variations in desorption of DDT in the three soils in similar experimental conditions. DDT dissolution in SDS and soil organic matter removal employing the ultrasonic-enhanced organic matter roll-up mechanism emerged as the two best possible methods of DDT desorption. The method offers a practical, potentially low-cost alternative to high volume, costly, hazardous solvent extraction of DDT.     

Re-sequencing of vrs1 and int-c loci shows that labile barleys (Hordeum vulgare convar. labile) have a six-rowed genetic background

Labile-barleys (Hordeum vulgare convar. labile (Schiem.) Mansf.) are found in the highlands of Ethiopia, Eretria and North India-Pakistan districts. They represent a distinct spike form showing row-type alterations even within individual spikes of the same genotypes. Variation at the six-rowed spike 1 (vrs1) locus is sufficient to control barley lateral spikelet fertility, which is also modified by alleles at the intermedium-c (int-c) locus. This study aimed at re-sequencing these two loci to investigate whether labile-barleys have a two-rowed genetic background, resulting in increased lateral spikelet fertility, or show reduced lateral spikelet fertility if they possess a six-rowed genetic background. The Vrs1 re-sequencing results of 221 supposedly labile-barley accessions from Ethiopia revealed 13 accessions with two novel vrs1.a1 haplotypes. Following the current nomenclature of vrs1 haplotypes, the new haplotypes were named as haplotypes 66 and 67. Re-sequencing at the int-c locus showed that 118 of the labile-barleys possessed the previously described Int-c.a allele but only one accession was found having a novel Int-c.a haplotype in the homozygous state (termed Int-c.a haplotype1; Hap_1). Interestingly, 101 labile-barleys carried the Int-c.a allele and Int-c.a haplotype1 simultaneously, suggesting maintained heterozygosity or recent gene duplication at this locus. Only one accession had a two-rowed haplotype (Vrs1.b3, int-c.b1) and one accession possessed the Vrs1.t (deficiens) and Int-c.a alleles (six-rowed). These two accessions were considered as misclassified labile genotypes and not included in further analysis. Thus, these results confirmed that all of the 219 labile accessions studied in this work showed six-rowed alleles at vrs1 but reduced lateral spikelet fertility. This reduction is most likely caused by the recessive labile (lab) locus which we are in the process to characterize further.     

Effects of an oil-based substrate (The Water Cleanser™) and bacterial additives on nitrogen and phosphorous dynamics in freshwater crayfish (Cherax cainii,Austin and Ryan 2002) aquaculture

Two experiments were conducted to evaluate the efficacy of an oil-based substrate, The Water Cleanser? (TWC). The first experiment studied the effects two substrates of different oil composition (TWC, TWC?+), and a commercial bacterial additive (Bio-Aid) on concentrations of nitrogen and phosphorous in indoor aquaria. The second experiment studied the effects of TWC, a bacterial additive, and a combination (TWC?+?B) on concentrations of nitrogen and phosphorous, phytoplankton abundance and diversity in outdoor freshwater crayfish (Cherax cainii, Austin and Ryan, Invertebr Syst 16:357–367, 2002) tanks. In the first experiment, the concentration of TAN decreased more rapidly with Bio-Aid, whilst the maximum concentrations of NO₂-N and NO₃-N were reduced with the substrates. The concentration of orthophosphate was reduced in aquaria with TWC?+?. In the second experiment, concentrations of TAN, NO₂-N, NO₃-N and total phosphate were not significantly affected by TWC. After addition of TWC?+?B, there was a significant decrease in the concentrations of nitrate and total phosphate, and a higher abundance of phytoplankton was maintained than with other treatments. Additionally, a population Bacillus sp. was found on the substrate surface. TWC had no adverse effects on phytoplankton abundance or diversity, or C. cainii physiology, weight gain or survival. TWC and TWC?+?were effective bioremediators of eutrophic water, whilst a combination of TWC?+?B was effective in short term bioremediation and in promoting phytoplankton abundance in C. cainii tank culture.