ABSTRACT
The characteristics of nitrate horizontal transport in a major paddy soil, Wu Shan soil in the Tai Lake region, were studied. The concentration of nitrate during horizontal movement decreased with the increasing in distance from the tracer source, the change following a logarithmic function. The concentration of the nitrate was strongly correlated with the soil moisture content, as an exponential function. The horizontal transport velocity of nitrate was significantly correlated with the distance of the tracer source as power function. Therefore, the velocity of nitrate horizontal transport was controlled by the concentration gradient of nitrate, and soil water potential gradient from beginning to the 20 cm mark in the horizontal column. However, the velocity of nitrate horizontal was stable beyond 20 cm, where it was controlled by soil matric potential.
Subject(s)
Nitrates/metabolism , Soil Pollutants/metabolism , Soil/analysis , Water Pollutants, Chemical/metabolism , Algorithms , China , Diffusion/drug effects , Equipment Design , Osmotic Pressure/drug effects , Water/pharmacology , Water MovementsABSTRACT
The reactions of ferulic acid and its derivatives with hydrogen peroxide and peracetic acid in lignin-retaining bleaching conditions have been investigated to determine their susceptibility to oxidative degradation. The conjugated side chain of ferulic acid and its etherified or esterified derivative was shown to be fairly stable, especially to hydrogen peroxide. The major reaction was trans-cis isomerization that possibly involved a radical mechanism but did not cause bond cleavage. The peracetic acid reaction increased the rate of trans-cis isomerization and was also accompanied by a minor cleavage of the side chain. Esterification did not have a substantial effect on the reactivity of ferulic acid, but 4-O-etherification significantly stabilized it against these two oxidants. By contrast, aldehyde substitution tremendously enhanced the susceptibility of the cinnamyl side chain to oxidative degradation, as evidenced by an intensive degradation of coniferaldehyde.
Subject(s)
Coumaric Acids/chemistry , Hydrogen Peroxide/chemistry , Lignin/chemistry , Peracetic Acid/chemistry , Kinetics , Models, Chemical , Oxidation-Reduction , Spectrophotometry, UltravioletABSTRACT
OBJECTIVE: To determine the prevalence rate of primary Sjögren's syndrome (SS) in a community population of 2066 adults in a Beijing suburban village, and 100 inpatients, who were not necessarily admitted for rheumatic diseases. METHODS: Questionnaire and serological studies of antinuclear antibodies, rheumatoid factor, and anti-SSA, anti-SSB antibodies were done. Possible positive subjects were given eye and oral examinations for objective evidence of xerostomia and keratoconjunctivitis sicca. RESULTS: According to the Copenhagen criteria, the prevalence rate of primary Sjögren's syndrome in China was 0.77%, and it was 0.33% by modified San Diego criteria. In 100 inpatients, we found 4 cases of primary Sjögren's syndrome by Copenhagen criteria, and one case by modified San Diego criteria. CONCLUSION: Primary Sjögren's syndrome is not a rare disease in China, but most cases are overlooked or misdiagnosed.
