Modelling Replicated Weed Growth Data using Spatially-varying Growth Curves

Weed growth in agricultural fields constitutes a major deterrent to the growth of crops, often resulting in low productivity and huge losses for the farmers. Therefore, proper understanding of patterns in weed growth is vital to agricultural research. Recent advances in Geographical Information Systems (GIS) now allow geocoding of agricultural data, which enable more sophisticated spatial analysis. Our current application concerns the development of statistical models for conducting spatial analysis of growth patterns in weeds. Our data comes from an experiment conducted in Waseca, Minnesota, that recorded growth of the weed Setariaspp. We capture the spatial variation in Setaria spp. growth using spatially-varying growth curves. An added challenge is that these designs are spatially replicated, with each plot being a lattice of sub-plots. Therefore, spatial variation may exist at different resolutions – a macro level variation between the plots and micro level variation between the sub-plots nested within each plot. We develop a Bayesian hierarchical framework for this setting. Flexible classes of models result which are fitted using simulation-based methods.     

Temperature and salinity adaptation in the purple shore crab Hemigrapsus nudus: An in vitro physiological study with excised gills

The alkali-soluble polysaccharides of the cell wall from 7 different marine diatoms were shown to contain the monosaccharides rhamnose, fucose, galactose, mannose and xylose. The relative amounts of rhamnose and fucose varied widely from one species to another, from the very rhamnose-rich Chaetoceros affinis to Thalassiosira gravida, where no rhamnose was found. All Chaetoceros species were found to have a high content of rhamnose. Also the proportion of mannose to galactose varied widely from species to species. The observed change in monomer composition from the logarithmic to the stationary growth phase is explained by assuming the alkali-soluble fraction to be a mixture of polysaccharides. The soluble, extracellular polysaccharides from 4 of the diatoms were also investigated. The products from C. affinis and C. curvisetus were homogeneous and composed of only 3 monomers: rhamnose, fucose and galactose. The extracellular polysaccharide composition in all species investigated was quite different from the composition of the cellular alkali-soluble fraction. The ecological aspects of these soluble polysaccharides may prove of considerable interest.     

Occupational hygiene in a Finnish drum composting plant

Bioaerosols (microbes, dust and endotoxins) and volatile organic compounds (VOCs) were determined in the working air of a drum composting plant treating source-separated catering waste. Different composting activities at the Oulu drum composting plant take place in their own units separated by modular design and constructions. Important implication of this is that the control room is a relatively clean working environment and the risk of exposure to harmful factors is low. However, the number of viable airborne microbes was high both in the biowaste receiving hall and in the drum composting hall. The concentration (geometric average) of total microbes was 21.8 million pcs/m3 in the biowaste receiving hall, 13.9 million pcs/m3 in the drum composting hall, and just 1.4 million pcs/m3 in the control room. Endotoxin concentrations were high in the biowaste receiving hall and in the drum composting hall. The average (arithmetic) endotoxin concentration was over the threshold value of 200 EU/m3 in both measurement locations. In all working areas, the average (arithmetic) dust concentrations were in a low range of 0.6-0.7 mg/m3, being below the Finnish threshold value of 5 mg/m3. In the receiving hall and drum composting hall, the concentrations of airborne microbes and endotoxins may rise to levels hazardous to health during prolonged exposure. It is advisable to use a respirator mask (class P3) in these areas. Detected volatile organic compounds were typical compounds of composting plants: carboxylic acids and their esters, alcohols, ketones, aldehydes, and terpenes. Concentrations of VOCs were much lower than the Finnish threshold limit values (Finnish TLVs), many of the quantified compounds exceeded their threshold odour concentrations (TOCs). Primary health effects due VOCs were not presumable at these concentrations but unpleasant odours may cause secondary symptoms such as nausea and hypersensitivity reactions. This situation is typical of composting plants where the workers are exposed to dozens of VOCs simultaneously. The odour units (OU/m3) were measured using olfactometer. The numbers were 23,000 OU/m3 at the output end of the composting drum and 6300 OU/m3 in the exhaust pipe. Inside the composting hall, the number of odour units was 500 and 560 OU/m3.     

Impact of crystalline and amorphous iron- and aluminum hydroxides on mechanisms of phosphate adsorption and desorption

Fourier-transform infrared(FT-IR) spectroscopic experiments were carried out during phosphate adsorption on highly crystalline gibbsite, poorly crystalline 2-line-ferrihydrite and amorphous iron–aluminum–hydroxide mixtures in the molar ratio 1:0, 10:1, 5:1, 1:1, 1:5, 1:10 and 0:1. The OH stretching vibrational bands were utilized to analyze changes in structural and surface OH groups during adsorption, because the position of characteristic P\O vibrational bands can shift depending on reaction conditions, pH or adsorbed phosphate content.Adsorption and desorption kinetics were studied at pH6 and different initial phosphate concentrations to achieve varying phosphate coverage on the mineral surfaces. For gibbsite the formation of AlHPO_4 and Al_2HPO_4 can be assumed, while for ferrihydrite, a FeHPO_4 or Fe_2PO_4 complex and the precipitation of FePO_4 with longer equilibration time were proposed.Fe_2HPO_4 or a Fe_2PO_4 surface complex was deduced for Fe-hydroxides, an AlH_2PO_4 surface complex was identified for Al-hydroxide, and both displayed either hydrogen bonds to neighboring hydroxyl groups or hydrogen bonds to outer-sphere complexes. Fe:Al-hydroxide mixtures with high Al ratios showed a low phosphate desorption rate, while ferrihydrite and the Fe:Al-hydroxide mixtures with high Fe ratios had almost negligible desorption rates. It was concluded that within the weakly associated amorphous FeO(OH) materials, FePO_4 precipitated, which was bound by outer-sphere hydrogen bonds. With high Al ratios, desorption increased, which indicated weaker phosphate binding of both inner-sphere and outer-sphere complexes and hence, either no or minor quantities of precipitate. Ferrihydrite showed a more rigid structure and a lower extent of precipitation compared to amorphous Fe-hydroxide.     

Skeletal Sr content and density in Porites spp. in relation to environmental factors

The coral genus Porites was investigated to evaluate the use of skeletal strontium content as a recorder of seasonal and annual temperature oscillations. In the Hawaiian archipelago, the mean annual water temperature fluctuates by ±0.5C°, with seasonal temperature ranges of 4 to 8C°; the resolution of the Sr thermometer appears to be ±1.5C°. Of this error term, ±0.7C° is analytical, the remainder is biological. Corals from some locations yield temperatures which are consistently offset from the Sr vs temperature calibration line, suggesting genetic population differences. Analysis of cores collected in 1980 from Hawaiian Porites spp. showed no discernible long-term trends over a 100 yr period. Although absolute temperatures are poorly resolved, subannual oscillations in skeletal Sr values accurately reflect recorded seasonal temperature variations. The most useful application of the Sr thermometer is in deciphering the skeletal density band pattern. Subannual oscillations in Sr-temperature values when correlated with density values showed a consistent pattern. When the sections chosen for x-radiography closely followed the growth axis, an abrupt shift from minimum to maximum skeletal density was evident in September/October each year, followed by a gradual decrease in density. The density pattern, shown by microdensitometry, is independent of latitude or temperature range over the Hawaiian archipelago. The annual density shift coincides with high but declining water temperature and solar insolation. If low-density growth represents optimum calcification conditions, the density shift in Hawaiian Porites spp. reflects a change in conditions from optimal to suboptimal. Analyses of samples from other Indo-Pacific locations confirm the generality of this density pattern and suggest a complex relationship between density and environmental light and temperature.Hawaii Institute of Geophysics Contribution No. 1209; Hawaii Institute of Marine Biology Contribution No. 618