Mode of action of thiocyanates and iodides in aminotriazole formulations

Ammonium thiocyanate ( I ) was shown to inhibit the oxidation of aminotriazole (3-amino-1,2,4-triazole) in two free-radical generating systems: (a) riboflavin photo-sensitised oxidation; and (b) oxidation by hydroxyl radicals. Evidence from in-vitro studies is presented to show that I could enhance aminotriazole performance by being preferentially oxidised within the leaf, thereby preventing aminotriazole free-radical formation and subsequent conjugation with amino acids and other compounds. This opens up the possibility of a whole new range of additives which could enhance translocation by inhibiting free-radical reactions. A comparison of possible inhibitors revealed that cyanides, iodides and perhaps bromides may be of use in this respect. In addition to inhibiting free-radical reactions, I and potassium iodide ( II ) were shown to have a considerable effect on the uptake of aminotriazole by bean leaves (Phaseolus vulgaris var. Canadian Wonder). In the absence of additives, uptake of aminotriazole was negligible (1.8%); in the presence of a 1:1 molar ratio of I or II , uptake of aminotriazole was increased to 36.6% and 54.2% respectively. At a 3:1 molar ratio of additive:aminotriazole, the respective figures were 63.5% and 81.0%. II appeared to be the more efficient of the two additives at higher humidity. However, the results and observations indicated that the situation may be reversed under low-humidity conditions.     

AORTOILIAC THROMBUS SECONDARY TO A MINERALIZED ARTERIOSCLEROTIC LESION

A 12-year-old, neutered female, Siberian Husky dog presented with a hind limb weakness of one month duration. To facilitate making a diagnosis multiple imaging modalities were performed. These modalities included radiography, ultrasonography, magnetic resonance imaging (MRI), magnetic resonance angiography (MRA) and selective angiography of the abdominal aorta. In this dog, the MRI/MRA studies provided the first documentation of the external iliac thrombi and the collateral circulation via the lumbar arteries. At necropsy, an aortoiliac thrombus caused by a mineralized arteriosclerotic plaque was noted.     

Tissue culture method affects ex vitro growth and development of loblolly pine

Loblolly pine (Pinus taeda L.) propagules initiated adventitiously from cotyledons and via axillary-fascicular micropropagation from epicotyls were compared to seedlings grown from the same open-pollinated seedlot. Greenhouse and early field results indicate that unlike tissue culture propagules of cotyledon-origin, propagules originating via axillary-fascicular micropropagation from epicotyls do not display early reduced growth relative to seedlings. Further, axillary-fascicular micropropagules derived from cotyledon-origin adventitious shoots displayed early reduced growth. Early reduced growth and other differences between tissue culture propagules and seedlings previously observed in field plantings appear to be inherent to the cotyledon system of propagation and do not necessarily occur when other tissue culture procedures are used for propagation.     

Outgassing behavior and composition of comet C/1999 S4 (LINEAR) during its disruption

The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (相似文献   

Land-cover change and human population trends in the greater Serengeti ecosystem from 1984–2003

The growth of human populations around protected areas accelerates land conversion and isolation, negatively impacting biodiversity and ecosystem function, and can be exacerbated by immigration. It is often assumed that immigration around protected areas is driven by attraction in the form of economic benefits, but in many cases, people may be pushed from their areas of origin toward protected areas. Mitigating the effects of immigration around protected areas necessitates understanding the actual mechanisms causing it, which can be aided by analysis of patterns of land-cover change. Our goal was to identify the reasons for human population growth and land-cover change around the protected areas in the greater Serengeti ecosystem (henceforth “the park”), and to relate agricultural conversion from 1984–2003 to trends in human demography. We found that conversion of natural habitats to agriculture was greatest closer to the park (up to 2.3% per year), coinciding with the highest rates of human population growth (3.5% per year). Agricultural conversion and population growth were greatest where there was less existing agriculture, and population density was lowest. Lack of unfarmed land farther from the park, coupled with greater poverty near the park, suggest that movement away from areas with high population densities and land scarcity was likely driving immigration near the park, where arable land was available. Our results are essential for conservation planning for one of Africa’s hallmark ecosystems, and should encourage further examination of population growth and land-cover trends near protected areas throughout the developing world.     

Magnesium deficiency in Douglas-fir and Grand fir growing on a sandy outwash soil amended with sewage sludge

Soil and plant samples were collected from chlorotic plantations of Grand fir (Abies grandis) and Douglas-fir (Pseudotsuga menziesii) in Winter, 1989. The soils had been amended in 1981 with an average of 300 dry Mg ha^?1 of municipal sewage sludge. The sludge amendment resulted in an N application rate of approximately 8000 kg ha^?1. Foliage analysis indicated a severe Mg deficiency (0.25 g kg^?1 in sludge-treated vs. 0.93 g kg^?1 in untreated area) might be the cause of chlorosis. No other nutrient showed concentrations in the deficient or toxic ranges. Trace metal levels in foliage were elevated significantly for Ni, Cd and Cr in sludge-treated sites, but not toxic levels. Soil samples taken to a depth of 1.4 m indicated the potential for soil acidification (up to 0.9 pH unit) in soil surface horizons. In addition, exchangeable Ca, Mg and K may have been depleted in surface horizons. Exchangeable Al and Fe were greater in the surface of sludge-treated sites. These observations and the loss of much of the nitrogen added during the sludge amendment indicated that nitrification and cation leaching was likely the mechanism for acidification and depletion of exchangeable cations. Fertilization of the plantation with MgSO₄ or dolomitic limestone was carried out in Spring 1990. New foliage collected in June, 1990 was non-chlorotic and significantly higher in Mg concentration than unfertilized foliage (1.1. vs. 0.7 g kg^?1, respectively). Results of this study indicate that it is important to assess the potential for initiating a nutrient deficiency due to secondary effects of sludge application in forest systems.     

Multiresidue assay for benzimidazole anthelmintics by liquid chromatography and confirmation by gas chromatography/selected-ion monitoring electron impact mass spectrometry

A multiresidue method utilizing all-disposable labware has been developed for 8 benzimidazole anthelmintics from ovine, bovine, and swine muscle and liver tissues. After an initial extraction with ethyl acetate and subsequent evaporation, a 3-component extraction using hexane, ethanol, and 0.2N HCl was used for final cleanup. Clean extracts were produced for separation and determination by reverse-phase liquid chromatography at 298 nm, using methanol and aqueous buffer as mobile phase. A synthesized internal standard, 2-(n-butylmercapto)benzimidazole, was used for quantitation of all drugs. Results are included along with statistical information verifying the performance of the method. Spiked control tissues and incurred drug tissues were used for an intralaboratory study with a concentration range of 50-1470 ppb. A series of standard curves at 0, 50, 100, and 200 ppb were analyzed. Overall recovery at the 100 ppb level averaged 92% (CV 8%) in liver tissues, across all 3 species and 88% (CV 5%) in muscle tissues across all 3 species. Results were confirmed by gas chromatography/mass spectrometry with acid hydrolysis of the remaining extract in 2N HCl followed by re-extraction of the amine and derivatization to the tert-butyldimethylsilyl derivative. The anthelmintics were identified by gas chromatography/selected ion monitoring electron-impact mass spectrometry. Ion ratio measurements were taken and compared to standard material. CVs averaged 10% or less for all drugs tested.